Showing 1–50 of 101 results for author: Wu, Q

A broadband, individually addressing two- and three-dimensional photonic integrated circuit for trapped-ion qubit control

Authors: Daniel Klawson, Yiyang Zhi, Bingran You, Michael Bareian, Elijah Mossman, Chun-Yuan Fan, Arkadev Roy, Ke Sun, Jason Lee, Sung Cheol Yoon, Qiming Wu, Lai Jiang, Wenjun Ke, Weiwei Wu, Sirui Tang, Zachary Wall, Jiaxiang Wang, Louis Paul Romero, Sam Vizvary, Steven Diaz, Eric R. Hudson, Wesley C. Campbell, Hartmut Haeffner, Ming C. Wu

Abstract: Trapped ions provide a high-fidelity platform for quantum information processing, yet delivery of multiple, distinct wavelengths across large networks of interaction zones remains a bottleneck. Conventional free-space light delivery lacks scalability, while on-chip grating couplers suffer from narrow operational bandwidth that increases circuit footprint and optical interfacing complexity. Here we… ▽ More Trapped ions provide a high-fidelity platform for quantum information processing, yet delivery of multiple, distinct wavelengths across large networks of interaction zones remains a bottleneck. Conventional free-space light delivery lacks scalability, while on-chip grating couplers suffer from narrow operational bandwidth that increases circuit footprint and optical interfacing complexity. Here we show a broadband photonic integrated circuit capable of addressing individual ions. The circuit combines a planar waveguide lens with a micromirror fabricated using two-photon polymerization at wafer scale. This implementation can address three individual ions from $λ$ = 405 - 880 nm with -27 dB average intensity crosstalk at $5\,μ\mathrm{m}$ pitch. We trap $^{40}\mathrm{Ca}^{+}$ and $^{138}\mathrm{Ba}^{+}$ ions above such devices, characterize optical crosstalk with barium ions, and demonstrate individual repumping of calcium ions. This monolithic photonic architecture brings broadband addressing in an on-chip modality to trapped-ion technology. More generally, integrating additive manufacturing into quantum devices is poised to unlock expanded design space for implementing novel quantum architectures. △ Less

Submitted 27 July, 2026; originally announced July 2026.

Comments: 17 pages, 5 figures

Spatial nonlocality imaging via metasurface

Authors: Jian Li, Zi-Mu Fan, Qing-Yuan Wu, Wen-Kai Yu, Zhe Meng, Xing-Yan Fan, Wen-Hao Wang, Jie Ma, Xia Guo, An-Ning Zhang

Abstract: Bell nonlocality is both a defining signature of entanglement and a key quantum information resource. However, visualizing and certifying nonlocal correlations across a spatially multimode photonic field remains challenging due to the rapidly growing measurement cost of spatially resolved projective tests. To address this issue, we build a spatial nonlocality imaging scheme that directly reveals t… ▽ More Bell nonlocality is both a defining signature of entanglement and a key quantum information resource. However, visualizing and certifying nonlocal correlations across a spatially multimode photonic field remains challenging due to the rapidly growing measurement cost of spatially resolved projective tests. To address this issue, we build a spatial nonlocality imaging scheme that directly reveals the spatial distribution of quantum nonlocality by integrating a metasurface that performs parallel polarization projections with a quantum-adaptive neural network. Spatially resolved Clauser--Horne--Shimony--Holt (CHSH) tests are realized over a 400-pixel biphoton field using an average of only 1.7 detected coincidence pairs per pixel per basis. This approach yields a nonlocality image that maps the two-dimensional spatial distribution of Bell violations across the optical field and reveals the target-state-dependent spatial evolution of Bell violations. It provides a highly resource-efficient route to large-scale Bell certification and opens new possibilities for exploiting spatially multimode entanglement in quantum imaging, quantum networking, and scalable photonic quantum technologies. △ Less

Submitted 20 July, 2026; originally announced July 2026.

Comments: 18 pages, 5 figures, with 21 pages of Supplementary Materials. Comments are welcome; please contact the corresponding authors for inquiries

Nonreciprocal Photon Blockade in an Asymmetric Cavity

Authors: Shao-Xiong Wu, Jin-Na Fan, Dan Yan, Cheng-Hua Bai, Qiannan Wu, Mengwei Li

Abstract: We propose a scheme to realize tunable and strong nonreciprocal photon blockade (PB) in an asymmetric Fabry-Pérot cavity. The setup consists of a single-mode optical cavity trapping a two-level atom, with the cavity coherently driven by a laser and the atom pumped by an auxiliary control field of the same frequency. By engineering quantum interference between multiple excitation pathways by adjust… ▽ More We propose a scheme to realize tunable and strong nonreciprocal photon blockade (PB) in an asymmetric Fabry-Pérot cavity. The setup consists of a single-mode optical cavity trapping a two-level atom, with the cavity coherently driven by a laser and the atom pumped by an auxiliary control field of the same frequency. By engineering quantum interference between multiple excitation pathways by adjusting the amplitude and relative phase of the control laser, we identify two distinct optimal control conditions that enable directional suppression of two-photon states. Under optimal control conditions, strong nonreciprocal PB is achieved, with a nonreciprocal ratio exceeding 30 dB over a broad operational bandwidth. The proposed protocol requires only standard coherent laser sources and is compatible with current cavity QED experimental setups, offering a practical and scalable platform for nonreciprocal quantum photonics. △ Less

Submitted 8 June, 2026; originally announced June 2026.

Journal ref: Advanced Quantum Technologies, 2026; 9: e70324

Adjusting the left-handedness in a cold $^{87}$Rb atom via multiple parameter modulation

Authors: ShunCai Zhao. Qi-Xuan Wu, Kun Ma

Abstract: We demonstrate the adjusting left-handedness in the cold \(^{87}\)Rb atom by its number density, the strong coupling field and two incoherent pumping fields. The results show that more dense \(^{87}\)Rb atoms and more stronger coupling field can influence the left-handedness more greatly, while the increasing two incoherent pumping fields construct the negative magnetic response but depress the ne… ▽ More We demonstrate the adjusting left-handedness in the cold \(^{87}\)Rb atom by its number density, the strong coupling field and two incoherent pumping fields. The results show that more dense \(^{87}\)Rb atoms and more stronger coupling field can influence the left-handedness more greatly, while the increasing two incoherent pumping fields construct the negative magnetic response but depress the negative electric response. The left-handedness adjusted by multiple parameter in the cold \(^{87}\)Rb atomic system provides the flexibility and feasibility for the coming experiment. △ Less

Submitted 3 May, 2026; originally announced May 2026.

Comments: 6 pages, 3 figures

Journal ref: Chinese Journal of Physics 54 (2016) 756-760

Parameter trajectory engineering for state transfer and quantum sensing in non-Hermitian two-level systems

Authors: Qi-Cheng Wu, Yan-Hui Zhou, Biao-liang Ye, Tong Liu, Yi-Hao Kang, Qi-Ping Su, Chui-Ping Yang

Abstract: Exceptional points (EPs) in non-Hermitian systems give rise to enhanced sensitivity and chiral state transfer, which are important for quantum technologies. Although parameter trajectories encircling EPs can control symmetric and chiral state transfer, their robustness against practical perturbations and their role in quantum sensing remain largely unexplored. Here, we study three time-modulated p… ▽ More Exceptional points (EPs) in non-Hermitian systems give rise to enhanced sensitivity and chiral state transfer, which are important for quantum technologies. Although parameter trajectories encircling EPs can control symmetric and chiral state transfer, their robustness against practical perturbations and their role in quantum sensing remain largely unexplored. Here, we study three time-modulated parameter loops in a non-Hermitian two-level system to show how trajectory design governs state-transfer symmetry, robustness, and sensing performance. Trajectories avoiding the EP support robust symmetric transfer, while those encircling the EP yield chiral transfer governed by the topological winding number, whose robustness depends on the distance to the EP and the encircling direction. For quantum sensing, trajectory engineering enables tuning of sensitivity amplitude, time window, and parameter selectivity in both eigenvalue-based and eigenstate-based sensors. Notably, eigenstate-based sensing achieves full parameter selectivity that is unattainable with eigenvalue-based methods. Our results establish a quantitative connection between trajectory topology and system dynamics, providing a unified framework for robust state-transfer protocols and high-performance quantum sensors. △ Less

Submitted 25 March, 2026; originally announced March 2026.

Comments: 10 pages, 7 figures

Journal ref: Physical Review A 114, 022610 (2026)

Real-Time Magnetic Field Sensing based on Microwave Frequency Modulated Photocurrent of Nitrogen-Vacancy Centers in Diamond

Authors: Xuan-Ming Shen, Qilong Wu, Huihui Yu, Pei-Nan Ni, Qing Lou, Chao-Nan Lin, Xun Yang, Chong-Xin Shan, Yuan Zhang

Abstract: While photoelectric detection of magnetic resonance (PDMR) can be applied to miniaturize nitrogen-vacancy (NV) center-based quantum sensors, real demonstration of PDMR-based magnetic field sensing remains as a distinctive challenge. To tackle this challenge, in this article, we fabricate diamond samples with electrodes and microwave antenna on the surface, and realize PDMR by detecting photocurren… ▽ More While photoelectric detection of magnetic resonance (PDMR) can be applied to miniaturize nitrogen-vacancy (NV) center-based quantum sensors, real demonstration of PDMR-based magnetic field sensing remains as a distinctive challenge. To tackle this challenge, in this article, we fabricate diamond samples with electrodes and microwave antenna on the surface, and realize PDMR by detecting photocurrent in picoampere range via various lock-in amplifying modes. We obtain a theoretical and experimental sensitivity 397 nT/Hz and 921 nT/Hz of magnetic field detection in DC-10 Hz range with a laser intensity and microwave frequency modulation mode, respectively, and demonstrate for the first time, a real-time tracking of alternating magnetic field with a standard deviation of 1.5 uT. Furthermore, we investigate systematically the dependence of the PDMR contrast, linewidth and the sensitivity on the laser and microwave power, and find a perfect agreement with a master equation-based theory. Thus, our results represent a critical step forward in transitioning PDMR from a spectroscopic technique to a practical sensing modality. △ Less

Submitted 11 February, 2026; v1 submitted 8 February, 2026; originally announced February 2026.

Comments: 14 pages, 9 figures

Talking with a ghost: semi-virtual coupled levitated oscillators

Authors: Ronghao Yin, Yugang Ren, Deok Young Seo, Anoushka Sinha, Jonathan D. Pritchett, Qiongyuan Wu, James Millen

Abstract: Mesoscopic particles levitated by optical, electrical or magnetic fields act as mechanical oscillators with a range of surprising properties, such as tuneable oscillation frequencies, access to rotational motion, and remarkable quality factors. Coupled levitated particles display rich dynamics and non-reciprocal interactions, with applications in sensing and the exploration of non-equilibrium and… ▽ More Mesoscopic particles levitated by optical, electrical or magnetic fields act as mechanical oscillators with a range of surprising properties, such as tuneable oscillation frequencies, access to rotational motion, and remarkable quality factors. Coupled levitated particles display rich dynamics and non-reciprocal interactions, with applications in sensing and the exploration of non-equilibrium and quantum physics. In this work, we present a single levitated particle displaying coupled-oscillator dynamics by generating an interaction with a virtual or ``ghost'' particle. This ghost levitated particle is simulated on an analogue computer, and its properties can thus be dynamically varied. Our work represents a new angle on measurement-based bath engineering and physical simulation and, in the future, could lead to the generation of novel cooling mechanisms and complex physical simulation. △ Less

Submitted 27 January, 2026; v1 submitted 22 December, 2025; originally announced December 2025.

Comments: 16 pages, 7 figures, Comments are welcome!

Journal ref: Photonics 2026, 13(2), 117

Rational regulation strategies of interstitial localized electrons in electride: A density functional theory study

Authors: L. Zhang, D. Wang, H. Wang, J. Li, Y. F. Wang, Q. Wu, Hua Y. Geng

Abstract: As a class of electron-rich materials, electrides demonstrate promising applications in many fields. However, the required high pressure restricts the practical applications to some extent. This study reveals that the unique feature of electride, i.e., the localization of interstitial electrons, can be greatly enhanced and tuned by self-defective doping, applying tensile/compressive stress, or she… ▽ More As a class of electron-rich materials, electrides demonstrate promising applications in many fields. However, the required high pressure restricts the practical applications to some extent. This study reveals that the unique feature of electride, i.e., the localization of interstitial electrons, can be greatly enhanced and tuned by self-defective doping, applying tensile/compressive stress, or shear stress. Moreover, the requirement of orbital orthogonality between the valence and core electron wave functions, as well as the Pauli exclusion principle, should be the driven force for the electron interstitial localization; and the exertion of external pressure modifies the available space to accommodate the electronic wave functions, thus enhances the interstitial localization. These discoveries lay down the ground for searching for promising electrides that are practicable at ambient conditions. △ Less

Submitted 2 December, 2025; originally announced December 2025.

Comments: 33 pages, 7 figures, with supplementary material

Journal ref: Computational Materials Science 258 (2025) 114117

Efficient and Robust Spatial-to-Fiber Coupling forMultimode Quantum Networks via CascadedAdaptive Feedback Control

Authors: Ya Li, WanRu Wang, Weizhe Qiao, Qizhou Wu, Changqing Niu, Xiaolong Zou, Youxing Chen, Xin Guo

Abstract: Duan-Lukin-Cirac-Zoller (DLCZ)-based multimodequantum networks rely on efficient spatial-to-fiber coupling, yetenvironmental perturbations compromise this performance. Wedevelop a cascaded adaptive feedback control system integratedinto the quantum entanglement source preparation path.Leveraging a power-feedback hillclimbing algorithm, itdynamically regulates piezoelectric-actuated mirrors to achi… ▽ More Duan-Lukin-Cirac-Zoller (DLCZ)-based multimodequantum networks rely on efficient spatial-to-fiber coupling, yetenvironmental perturbations compromise this performance. Wedevelop a cascaded adaptive feedback control system integratedinto the quantum entanglement source preparation path.Leveraging a power-feedback hillclimbing algorithm, itdynamically regulates piezoelectric-actuated mirrors to achieveautonomous multi-dimensional beam alignment, Experimentsshow it rapidly boosts single-mode fiber (SMF) coupling efficieneyto over 70% within 20 seconds and entering the most efficient andstable transmission state after 75 seconds.Importantly, it enhancesthe stability of the atom-photon interfacecritical for quantumlight-matter interactionsproviding a practical framework forefficient, robust spatial light transmission in scalable quantumnetworks. △ Less

Submitted 13 October, 2025; originally announced October 2025.

Accurate and Effective Model for Coexistence of Classical and Quantum Signals In Optical Fibers

Authors: Lucas Alves Zischler, Çağla Özkan, Tristan Vosshenrich, Qi Wu, Giammarco Di Sciullo, Divya A. Shaji, Chiara Lasagni, Paolo Serena, Alberto Bononi, Amirhossein Ghazisaeidi, Chigo Okonkwo, Antonio Mecozzi, Cristian Antonelli

Abstract: The rising interest in quantum-level communication has resulted in proposals for coexistence schemes with classical signals within the same fiber optic channel, where the most recent proposals leverage novel fibers designed for space-division multiplexing (SDM) transmission. In all cases the large power difference between classical and quantum channels presents challenges for such schemes, as the… ▽ More The rising interest in quantum-level communication has resulted in proposals for coexistence schemes with classical signals within the same fiber optic channel, where the most recent proposals leverage novel fibers designed for space-division multiplexing (SDM) transmission. In all cases the large power difference between classical and quantum channels presents challenges for such schemes, as the classical signals generate interfering noise that corrupts the quantum signal. In this work, we discuss the main interference mechanisms in coexistence scenarios and provide a model to quantify their impact on the quantum signal quality. Analytical approximations in the model allow accurate and fast numerical solutions in the millisecond time-scale. The model accounts for out-of-band non-linear interference effects, namely spontaneous Raman scattering (SpRS) and four-wave-mixing (FWM) in both cases of single-mode and SDM fibers with weakly-coupled degenerate mode groups. Rayleigh and SpRS backscattering are considered in counter-propagating scenarios. Since broadband classical transmission is targeted, the model also accounts for the effect of stimulated Raman scattering (SRS)-induced power tilt. Use of the model in sample scenarios indicates that the interference noise power is minimized at the high end of the transmission band in both cases were the quantum is co- and counter-propagating with respect to the classical signals, with a preference of one or the other scheme depending on the link length and quantum signal center frequency. Our model reveals that FWM has negligible impact in counter-propagating schemes, but can be relevant in co-propagating schemes under certain scenarios. Nevertheless, the FWM interference can be mitigated by deallocating the classical signals adjacent to the quantum channel. △ Less

Submitted 3 October, 2025; originally announced October 2025.

Comments: Submitted for the Journal of Lightwave Technology

Fiber-integrated NV Magnetometer with Microcontroller-based Software Lock-in Technique

Authors: Qilong Wu, Xuan-Ming Shen, Yuan Zhang, Ying-Geng Shan, Hui-Hui Yu, Jing-Hao Zhang, Jiahui Chen, Yan Wang, Xun Yang, Yong-Zhi Tian, Lijun Wang, Chong-Xin Shan

Abstract: Fiber-integrated nitrogen-vacancy (NV) magnetometers possess high sensitivity, integration, and flexibility, and thus have been explored extensively for industrial applications. While most studies have focused on the optimization of the quantum sensing head, less attention has been paid to the frequently employed professional, expensive, and bulky electronics, which hinder their practical applicat… ▽ More Fiber-integrated nitrogen-vacancy (NV) magnetometers possess high sensitivity, integration, and flexibility, and thus have been explored extensively for industrial applications. While most studies have focused on the optimization of the quantum sensing head, less attention has been paid to the frequently employed professional, expensive, and bulky electronics, which hinder their practical applications. In this article, we fabricate a fiber-integrated NV magnetometer and develop a low-cost microcontroller-based software lock-in technique. In this technique, a microcontroller coordinates efficiently a microwave source chip and an analog-to-digital converter, and a program mimicking the lock-in mechanism realizes microwave frequency-modulated optically detected magnetic resonance of NV centers. As a result, with our setup and technique, we have realized the detection of weak magnetic field with a sensitivity of 93 nT/Hz^{1/2}, which is comparable to what obtained with bulky and professional devices. Furthermore, we demonstrated real-time magnetic field detection, achieving a standard deviation of 488 nT. Our work provides a novel and cost-effective technique for electronic miniaturization, thereby potentially accelerating the industrial application of NV magnetometers. △ Less

Submitted 2 October, 2025; originally announced October 2025.

QUASAR: Quantum Assembly Code Generation Using Tool-Augmented LLMs via Agentic RL

Authors: Cong Yu, Valter Uotila, Shilong Deng, Qingyuan Wu, Tuo Shi, Songlin Jiang, Lei You, Bo Zhao

Abstract: Designing and optimizing task-specific quantum circuits are crucial to leverage the advantage of quantum computing. Recent large language model (LLM)-based quantum circuit generation has emerged as a promising automatic solution. However, the fundamental challenges remain unaddressed: (i) parameterized quantum gates require precise numerical values for optimal performance, which also depend on mul… ▽ More Designing and optimizing task-specific quantum circuits are crucial to leverage the advantage of quantum computing. Recent large language model (LLM)-based quantum circuit generation has emerged as a promising automatic solution. However, the fundamental challenges remain unaddressed: (i) parameterized quantum gates require precise numerical values for optimal performance, which also depend on multiple aspects, including the number of quantum gates, their parameters, and the layout/depth of the circuits. (ii) LLMs often generate low-quality or incorrect quantum circuits due to the lack of quantum domain-specific knowledge. We propose QUASAR, an agentic reinforcement learning (RL) framework for quantum circuits generation and optimization based on tool-augmented LLMs. To align the LLM with quantum-specific knowledge and improve the generated quantum circuits, QUASAR designs (i) a quantum circuit verification approach with external quantum simulators and (ii) a sophisticated hierarchical reward mechanism in RL training. Extensive evaluation shows improvements in both syntax and semantic performance of the generated quantum circuits. When augmenting a 4B LLM, QUASAR has achieved the validity of 99.31% in Pass@1 and 100% in Pass@10, outperforming industrial LLMs of GPT-4o, GPT-5 and DeepSeek-V3 and several supervised-fine-tuning (SFT)-only and RL-only baselines. △ Less

Submitted 1 October, 2025; originally announced October 2025.

Observation of synchronization between two quantum van der Pol oscillators in trapped ions

Authors: Jiarui Liu, Qiming Wu, Joel E. Moore, Hartmut Haeffner, Christopher W. Wächtler

Abstract: Synchronization is a hallmark of collective behavior that emerges when nonlinear systems interact, spanning scales from mechanical oscillators to planetary orbits. As a universal phenomenon it underpins the study of complex systems and has far-reaching technological implications. While classical synchronization has a long and rich history, it has not been observed experimentally between multiple q… ▽ More Synchronization is a hallmark of collective behavior that emerges when nonlinear systems interact, spanning scales from mechanical oscillators to planetary orbits. As a universal phenomenon it underpins the study of complex systems and has far-reaching technological implications. While classical synchronization has a long and rich history, it has not been observed experimentally between multiple quantum limit-cycle oscillators despite a decade of theoretical investigations. We realize synchronization between two quantum van der Pol oscillators by engineering dissipation in a mixed-isotope trapped-ion quantum simulator. The synchronized state is encoded in a fixed relative phase between the oscillators that is inaccessible to local measurements and only revealed through joint readout of both oscillators, in stark contrast to the classical case where synchronization can be observed via individual phase measurements. We further show that the relative phase can be precisely controlled, and that the chain of two oscillators can synchronize to an external field, suggesting applications in sensing. Our results provide a promising pathway for studying more complex synchronized quantum dynamics beyond two oscillators, where a theoretical treatment becomes increasingly challenging, and it remains to be understood whether genuinely quantum features persist in such cases. △ Less

Submitted 18 November, 2025; v1 submitted 22 September, 2025; originally announced September 2025.

Journal ref: Phys. Rev. X 16, 021062 (2026)

Long-exposure Camera Readout for Coherent Control of Nitrogen-Vacancy Center Spins in Diamond

Authors: Jiahui Chen, Qilong Wu, Huihui Yu, Yi-Dan Qu, Yuan Zhang, Xun Yang, Chong-Xin Shan

Abstract: Camera-based wide-field quantum noise spectroscopy (QNS) with nitrogen-vacancy (NV) center spins in diamond can be used to extract DC and AC magnetic field noise with sub-micrometer spatial resolution, but its realization is currently limited by the conflict between the optimal optical spin readout time (normally below one microsecond) and the minimal camera exposure time (normally tens of microse… ▽ More Camera-based wide-field quantum noise spectroscopy (QNS) with nitrogen-vacancy (NV) center spins in diamond can be used to extract DC and AC magnetic field noise with sub-micrometer spatial resolution, but its realization is currently limited by the conflict between the optimal optical spin readout time (normally below one microsecond) and the minimal camera exposure time (normally tens of microsecond). In the present article, we demonstrate fully coherent control of NV center spins via Rabi oscillation, Ramsey, Hahn echo and relaxometry experiments, i.e. the core of QNS, with a home-built camera-based setup, and achieve an unexpectedly high contrast of 12% with an optical spin readout time of 500 microseconds. We explain the absence of the above conflict in our system with the optical spin readout mechanism under weak laser illumination, where spin-lattice relaxation and weak optical pumping result in a rather slow reduction of contrast with increasing integration time. The revealed mechanism is instructive for the construction of the wide-field QNS with a sCMOS or EMCCD camera, and its application in the studies of magnetic material or superconducting material. △ Less

Submitted 15 September, 2025; originally announced September 2025.

Comments: 14 pages, 7 figures

Bound states and the collective dynamics of Distant Quantum Emitters coupled to a chiral waveguide

Authors: Meng Qian Wu, Ge Sun, Jing Lu, Lan Zhou

Abstract: We consider two two-level quantum emitters (QEs) with separations on the order of the wavelength which are chirally coupled to a one-dimensional (1D) waveguide, and the electromagnetic field of the 1D waveguide has a direction-dependent velocity, which produces two field propagation phases on the dynamics of QEs. Their spontaneous process is examined for QEs having unequal emission rates to the wa… ▽ More We consider two two-level quantum emitters (QEs) with separations on the order of the wavelength which are chirally coupled to a one-dimensional (1D) waveguide, and the electromagnetic field of the 1D waveguide has a direction-dependent velocity, which produces two field propagation phases on the dynamics of QEs. Their spontaneous process is examined for QEs having unequal emission rates to the waveguide. It is found that radiation could be enhanced for both QEs, inhibited for both QEs, enhanced for one while inhibited for the other, completely suppressed for both QEs. In particular, the mechanism for radiation completely suppressed is the presence of a QE-photon bound state. △ Less

Submitted 13 September, 2025; originally announced September 2025.

Superradiant Echoes Induced by Multiple Re-phasing of NV Spin Sub-ensembles Grating at Room Temperature

Authors: Qilong Wu, Yuan Zhang, Huihui Yu, Chong-Xin Shan, Klaus Mølmer

Abstract: In this Letter, we propose that superradiant echoes can be achieved at room temperature by applying a laser illumination and a microwave Hahn echo sequence to a diamond with a high concentration of nitrogen-vacancy (NV) centers placed in a dielectric microwave cavity. We identify that the combined action of two microwave driving pulses and a free evolution imprints a phase grating among NV spin su… ▽ More In this Letter, we propose that superradiant echoes can be achieved at room temperature by applying a laser illumination and a microwave Hahn echo sequence to a diamond with a high concentration of nitrogen-vacancy (NV) centers placed in a dielectric microwave cavity. We identify that the combined action of two microwave driving pulses and a free evolution imprints a phase grating among NV spin sub-ensembles in frequency space, and multiple re-phasing of the grated spin sub-ensembles leads to multiple superradiant echoes through a collective coupling with the cavity. Furthermore, we show that the superradiant echoes can be actively tailored with the microwave pulses and the laser illumination by modifying the grating parameters, and the multiple re-phasing dynamics is analogous to the one leading to superradiant beats in optical clock system. In the future, the spin sub-ensembles grating and the resulting echoes can be further optimized with dynamical decoupling, which might pave the way for applications in quantum sensing. △ Less

Submitted 1 July, 2025; originally announced July 2025.

Scalable Trapped Ion Addressing with Adjoint-optimized Multimode Photonic Circuits

Authors: Melika Momenzadeh, Ke Sun, Qiming Wu, Bingran You, Yu-Lung Tang, Hartmut Häffner, Maxim Radikovich Shcherbakov

Abstract: Trapped-ion quantum computing requires precise optical control for individual qubit manipulation. However, conventional free-space optics face challenges in alignment stability and scalability as the number of qubits increases. Integrated photonics offers a promising alternative, providing miniaturized optical systems on a chip. Here, we propose a design for a multimode photonic circuit integrated… ▽ More Trapped-ion quantum computing requires precise optical control for individual qubit manipulation. However, conventional free-space optics face challenges in alignment stability and scalability as the number of qubits increases. Integrated photonics offers a promising alternative, providing miniaturized optical systems on a chip. Here, we propose a design for a multimode photonic circuit integrated with a surface-electrode ion trap capable of targeted and reconfigurable light delivery. Three closely positioned ions can be addressed using a focusing grating coupler that emits multimode light through electrode openings to ions trapped 80 $μ$m above the chip. Simulations show that the couplers achieve diffraction-limited spot with a 4.3 $μ$m beam waist along the trap axis and 2.2 $μ$m perpendicular to the trap axis. Controlled interference of the TE$_{\text{10}}$ and TE$_{\text{20}}$ modes results in crosstalk of -20 dB to -30 dB at ion separations of 5-8 $μ$m when addressing ions individually, and down to -60 dB when two of the three ions are addressed simultaneously. Additionally, the higher-order TE modes can offer a novel mechanism for driving spin-motion coupling transitions, potentially enabling alternative approaches to quantum gates and simulations. The proposed integrated platform offers a viable path for constructing large-scale trapped-ion systems, leveraging the benefits of nanophotonic design for precise and reliable ion manipulation. △ Less

Submitted 13 May, 2025; originally announced May 2025.

Comments: 23 pages, 9 figures

Enhanced quantum sensing in time-modulated non-Hermitian systems

Authors: Qi-Cheng Wu, Yan-Hui Zhou, Tong Liu, Yi-Hao Kang, Qi-Ping Su, Chui-Ping Yang

Abstract: Enhancing the sensitivity of quantum sensing near an exceptional point represents a significant phenomenon in non-Hermitian (NH) systems. However, the application of this property in time-modulated NH systems remains largely unexplored. In this work, we propose two theoretical schemes to achieve enhanced quantum sensing in time-modulated NH systems by leveraging the coalescence of eigenvalues and… ▽ More Enhancing the sensitivity of quantum sensing near an exceptional point represents a significant phenomenon in non-Hermitian (NH) systems. However, the application of this property in time-modulated NH systems remains largely unexplored. In this work, we propose two theoretical schemes to achieve enhanced quantum sensing in time-modulated NH systems by leveraging the coalescence of eigenvalues and eigenstates. We conduct a comprehensive analysis of the full energy spectrum, including both real and imaginary components, the population distribution of eigenstates, and various characteristics associated with optimal conditions for sensitivity enhancement. Numerical simulations confirm that eigenvalue-based quantum sensors exhibit a 9.21-fold improvement compared to conventional Hermitian sensors, aligning with the performance of existing time-independent NH sensors. Conversely, for eigenstate-based quantum sensors, the enhancement reaches up to 50 times that of conventional Hermitian sensors, surpassing the results of existing time-independent NH sensors. Moreover, the eigenstate-based sensor exhibits divergent susceptibility even when not close to an exceptional point. Our findings pave the way for advanced sensing in time-sensitive contexts, thereby complementing existing efforts aimed at harnessing the unique properties of open systems. △ Less

Submitted 6 June, 2025; v1 submitted 20 March, 2025; originally announced March 2025.

Comments: 15 pages, 10 figures

Journal ref: Chinese Journal of Physics 98, 1116 (2025)

Mitigation of birefringence in cavity-based quantum networks using frequency-encoded photons

Authors: Chengxi Zhang, Justin Phillips, Inder Monga, Erhan Saglamyurek, Qiming Wu, Hartmut Haeffner

Abstract: Atom-cavity systems offer unique advantages for building large-scale distributed quantum computers by providing strong atom-photon coupling while allowing for high-fidelity local operations of atomic qubits. However, in prevalent schemes where the photonic state is encoded in polarization, cavity birefringence introduces an energy splitting of the cavity eigenmodes and alters the polarization stat… ▽ More Atom-cavity systems offer unique advantages for building large-scale distributed quantum computers by providing strong atom-photon coupling while allowing for high-fidelity local operations of atomic qubits. However, in prevalent schemes where the photonic state is encoded in polarization, cavity birefringence introduces an energy splitting of the cavity eigenmodes and alters the polarization states, thus limiting the fidelity of remote entanglement generation. To address this challenge, we propose a scheme that encodes the photonic qubit in the frequency degree-of-freedom. The scheme relies on resonant coupling of multiple transverse cavity modes to different atomic transitions that are well-separated in frequency. We numerically investigate the temporal properties of the photonic wavepacket, two-photon interference visibility, and atom-atom entanglement fidelity under various cavity polarization-mode splittings and find that our scheme is less affected by cavity birefringence. Finally, we propose practical implementations in two trapped ion systems, using the fine structure splitting in the metastable D state of $\mathrm{^{40}Ca^{+}}$, and the hyperfine splitting in the ground state of $\mathrm{^{225}Ra^{+}}$. Our study presents an alternative approach for cavity-based quantum networks that is less sensitive to birefringent effects, and is applicable to a variety of atomic and solid-state emitter-cavity interfaces. △ Less

Submitted 6 March, 2025; originally announced March 2025.

Comments: 13 pages, 6 figures

Transfer of Fisher Information in Quantum Postselection Metrology

Authors: Zi-Rui Zhong, Xia-Lin Su, Xiang-Ming Hu, Ke-Xuan Chen, Hui-Lin Xu, Yan Zhang, Qing-Lin Wu

Abstract: Postselected weak measurement has shown significant potential for detecting small physical effects due to its unique weak-value-amplification phenomenon. Previous works suggest that Heisenberg-limit precision can be attained using only the optical coherent states. However, the measurement object is the distribution of postselection, limiting the practical applicability. Here, we demonstrate that t… ▽ More Postselected weak measurement has shown significant potential for detecting small physical effects due to its unique weak-value-amplification phenomenon. Previous works suggest that Heisenberg-limit precision can be attained using only the optical coherent states. However, the measurement object is the distribution of postselection, limiting the practical applicability. Here, we demonstrate that the output photons can also reach the quantum scale by utilizing the Fisher information transfer effect. In addition, we consider the insertion of a power-recycling cavity and demonstrate its positive impact on the distribution of postselection. Our results enhance the quantum metrological advantages of the postselection strategy and broaden its application scope. △ Less

Submitted 6 December, 2024; originally announced December 2024.

Comments: 6 pages, 4figures

Spread complexity and the saturation of wormhole size

Authors: Vijay Balasubramanian, Javier M. Magan, Poulami Nandi, Qingyue Wu

Abstract: Recent proposals equate the size of Einstein-Rosen bridges in JT gravity to spread complexity of a dual, double-scaled SYK theory (DSSYK). We show that the auxiliary ``chord basis'' of these proposals is an extrapolation from a sub-exponential part of the finite-dimensional physical Krylov basis of a spreading thermofield double state. The physical tridiagonal Hamiltonian coincides with the DSSYK… ▽ More Recent proposals equate the size of Einstein-Rosen bridges in JT gravity to spread complexity of a dual, double-scaled SYK theory (DSSYK). We show that the auxiliary ``chord basis'' of these proposals is an extrapolation from a sub-exponential part of the finite-dimensional physical Krylov basis of a spreading thermofield double state. The physical tridiagonal Hamiltonian coincides with the DSSYK approximation on the initial Krylov basis, but deviates markedly over an exponentially large part of the state space. We non-perturbatively extend the identification of ER bridge size and spread complexity to the complete Hilbert space, and show that it saturates at late times. We use methods for tridiagonalizing random Hamiltonians to study all universality classes to which large N SYK theories and JT gravities can belong. The saturation dynamics depends on the universality class, and displays ``white hole'' physics at late times where the ER bridge shrinks from maximum size to a plateau. We describe extensions of our results to higher dimensions. △ Less

Submitted 2 December, 2024; originally announced December 2024.

Comments: 29 pages, 8 figures

Efficient and controlled symmetric and asymmetric Bell-state transfers in a dissipative Jaynes-Cummings model

Authors: Qi-Cheng Wu, Yu-Liang Fang, Yan-Hui Zhou, Jun-Long Zhao, Yi-Hao Kang, Qi-Ping Su, Chui-Ping Yang

Abstract: Realizing efficient and controlled state transfer is necessary for implementing a wide range of classical and quantum information protocols. Recent studies have demonstrated that both asymmetric and symmetric state transfer can be achieved by encircling an exceptional point (EP) in non-Hermitian (NH) systems. However, the application of this phenomenon has been restricted to scenarios where an EP… ▽ More Realizing efficient and controlled state transfer is necessary for implementing a wide range of classical and quantum information protocols. Recent studies have demonstrated that both asymmetric and symmetric state transfer can be achieved by encircling an exceptional point (EP) in non-Hermitian (NH) systems. However, the application of this phenomenon has been restricted to scenarios where an EP exists in single-qubit systems and is associated with a specific type of dissipation. In this work, we demonstrate efficient and controlled symmetric and asymmetric Bell-state transfers by modulating system parameters within a Jaynes-Cummings model while accounting for atomic spontaneous emission and cavity decay. The effective suppression of nonadiabatic transitions enables a symmetric exchange of Bell states irrespective of the encircling direction. Furthermore, we report a counterintuitive finding: the presence of an EP is not indispensable for implementing asymmetric state transfers in NH systems. We achieve perfect asymmetric Bell-state transfers even in the absence of an EP, by dynamically orbiting around an approximate EP. Our work presents an approach to effectively and reliably manipulate entangled states with both symmetric and asymmetric characteristics, through the dissipation engineering in NH systems. △ Less

Submitted 25 March, 2025; v1 submitted 16 November, 2024; originally announced November 2024.

Comments: 7 pages, 6 figures

Journal ref: Chinese Phys. B 2025

Two types of quantum chaos: testing the limits of the Bohigas-Giannoni-Schmit conjecture

Authors: Javier M. Magan, Qingyue Wu

Abstract: There are two types of quantum chaos: eigenbasis chaos and spectral chaos. The first type controls the early-time physics, e.g. the thermal relaxation and the sensitivity of the system to initial conditions. It can be traced back to the Eigenstate Thermalization Hypothesis (ETH), a statistical hypothesis about the eigenvectors of the Hamiltonian. The second type concerns very late-time physics, e.… ▽ More There are two types of quantum chaos: eigenbasis chaos and spectral chaos. The first type controls the early-time physics, e.g. the thermal relaxation and the sensitivity of the system to initial conditions. It can be traced back to the Eigenstate Thermalization Hypothesis (ETH), a statistical hypothesis about the eigenvectors of the Hamiltonian. The second type concerns very late-time physics, e.g. the ramp of the Spectral Form Factor. It can be traced back to Random Matrix Universality (RMU), a statistical hypothesis about the eigenvalues of the Hamiltonian. The Bohigas-Giannoni-Schmit (BGS) conjecture asserts a direct relationship between the two types of chaos for quantum systems with a chaotic semiclassical limit. The BGS conjecture is challenged by the Poissonian Hamiltonian ensembles, which can be used to model any quantum system displaying RMU. In this paper, we start by analyzing further aspects of such ensembles. On general and numerical grounds, we argue that these ensembles can have chaotic semiclassical limits. We then study the Poissonian ensemble associated with the Sachdev-Ye-Kitaev (SYK) model. While the distribution of couplings peaks around the original SYK model, the Poissonian ensemble is not $k$-local. This suggests that the link between ETH and RMU requires of physical $k$-locality as an assumption. We test this hypothesis by modifying the couplings of the SYK Hamiltonian via the Metropolis algorithm, rewarding directions in the space of couplings that do not display RMU. The numerics converge to a $k$-local Hamiltonian with eigenbasis chaos but without spectral chaos. We finally comment on ways out and corollaries of our results. △ Less

Submitted 12 November, 2024; originally announced November 2024.

Comments: 20 pages, 6 Figures

Shortcuts to adiabatic state transfer in time-modulated two-level non-Hermitian systems

Authors: Qi-Cheng Wu, Jun-Long Zhao, Yan-Hui Zhou, Biao-Liang Ye, Yu-Liang Fang, Zheng-Wei Zhou, Chui-Ping Yang

Abstract: Nontrivial spectral properties of non-Hermitian systems can give rise to intriguing effects that lack counterparts in Hermitian systems. For instance, when dynamically varying system parameters along a path enclosing an exceptional point (EP), chiral mode conversion occurs. A recent study [Phys. Rev. Lett. 133, 113802 (2024)] demonstrates the achievability of pure adiabatic state transfer by speci… ▽ More Nontrivial spectral properties of non-Hermitian systems can give rise to intriguing effects that lack counterparts in Hermitian systems. For instance, when dynamically varying system parameters along a path enclosing an exceptional point (EP), chiral mode conversion occurs. A recent study [Phys. Rev. Lett. 133, 113802 (2024)] demonstrates the achievability of pure adiabatic state transfer by specifically selecting a trajectory in the system parameter space where the corresponding evolution operator exhibits a real spectrum while winding around an EP. However, the intended adiabatic state transfer becomes fragile when taking into account the effect of the nonadiabatic transition. In this work, we propose a scheme for achieving robust and rapid adiabatic state transfer in time-modulated two-level non-Hermitian systems by appropriately modulating system Hamiltonian and time-evolution trajectory. Numerical simulations confirm that complete adiabatic transfer can always be achieved even under nonadiabatic conditions after one period for different initialized adiabatic states, and the scheme remains insensitive to moderate fluctuations in control parameters. Therefore, this scheme offers alternative approaches for quantum-state engineering in non-Hermitian systems. △ Less

Submitted 5 November, 2024; v1 submitted 1 November, 2024; originally announced November 2024.

Comments: 7 pages, 6 figures

Journal ref: Physical Review A 111.022410 (2025)

Generation of strong mechanical squeezing through the joint effect of two-tone driving and parametric pumping

Authors: Xiao-Jie Wu, Huan-Huan Cheng, Qiannan Wu, Cheng-Hua Bai, Shao-Xiong Wu

Abstract: We propose an innovative scheme to efficiently prepare strong mechanical squeezing through utilizing the synergistic mechanism of two-tone driving and parametric pumping in an optomechanical system. By reasonable choosing the system parameters, the proposal highlights the following prominent advantages: the squeezing effect of the cavity field induced by the optical parametric amplifier can be tra… ▽ More We propose an innovative scheme to efficiently prepare strong mechanical squeezing through utilizing the synergistic mechanism of two-tone driving and parametric pumping in an optomechanical system. By reasonable choosing the system parameters, the proposal highlights the following prominent advantages: the squeezing effect of the cavity field induced by the optical parametric amplifier can be transferred to the mechanical oscillator, which has been squeezed by the two-tone driving, and the degree of squeezing of the mechanical oscillator will surpass that obtained by any single mechanism; the joint mechanism can enhance the degree of squeezing significantly and break the 3 dB mechanical squeezing limit, which is particularly evident in range where the red/blue-detuned ratio is sub-optimal; the mechanical squeezing achieved through this distinctive joint mechanism exhibits notable robustness against both thermal noise and decay of mechanical oscillator. Our project offers a versatile and efficient approach for generating strong mechanical squeezing across a wide range of conditions. △ Less

Submitted 20 September, 2024; originally announced September 2024.

Journal ref: Opt.Express 32. 35663 (2024)

Neuromorphic detection and cooling of microparticles in arrays

Authors: Yugang Ren, Benjamin Siegel, Ronghao Yin, Qiongyuan Wu, Jonathan D. Pritchett, Muddassar Rashid, James Millen

Abstract: Micro-objects levitated in a vacuum are an exciting platform for precision sensing due to their low dissipation motion and the potential for control at the quantum level. Arrays of such sensors would offer increased sensitivity, directionality, and in the quantum regime the potential to exploit correlation and entanglement. We use neuromorphic detection via a single event based camera to record th… ▽ More Micro-objects levitated in a vacuum are an exciting platform for precision sensing due to their low dissipation motion and the potential for control at the quantum level. Arrays of such sensors would offer increased sensitivity, directionality, and in the quantum regime the potential to exploit correlation and entanglement. We use neuromorphic detection via a single event based camera to record the motion of an array of levitated microspheres. We present a scalable method for arbitrary multiparticle tracking and control by implementing real-time feedback to {simultaneously cool the motion of three uncoupled microscale objects △ Less

Submitted 15 September, 2025; v1 submitted 1 August, 2024; originally announced August 2024.

Comments: Version 2

Journal ref: Nature Communications 16, 10658 (2025)

Entanglement-assist cyclic weak-value-amplification metrology

Authors: Zi-Rui Zhong, Xia-lin Su, Xiang-Ming Hu, Qing-lin Wu

Abstract: Weak measurement has garnered widespread interest for its ability to amplify small physical effects at the cost of low detection probabilities. Previous entanglement and recycling techniques enhance postselection efficiency and signal-to-noise ratio (SNR) of weak measurement from distinct perspectives. Here, we incorporate a power recycling cavity into the entanglement-assisted weak measurement sy… ▽ More Weak measurement has garnered widespread interest for its ability to amplify small physical effects at the cost of low detection probabilities. Previous entanglement and recycling techniques enhance postselection efficiency and signal-to-noise ratio (SNR) of weak measurement from distinct perspectives. Here, we incorporate a power recycling cavity into the entanglement-assisted weak measurement system. We obtain an improvement of both detection efficiency and Fisher information, and find that the improvement from entanglement and recycling occur in different dimensions. Furthermore, we analyze two types of errors, walk-off errors and readout errors. The conclusions suggest that entanglement exacerbates the walk-off effect caused by recycling, but this detriment can be balanced by proper parameter selection. In addition, power-recycling can complement entanglement in suppressing readout noise, thus enhancing the accuracy in the measurement results and recovering the lost Fisher information. This work delves deeper into the metrological advantages of weak measurement. △ Less

Submitted 6 June, 2024; originally announced June 2024.

Comments: 12 pages, 8 figures

Temporally multiplexed ion-photon quantum interface via fast ion-chain transport

Authors: Bingran You, Qiming Wu, David Miron, Wenjun Ke, Inder Monga, Erhan Saglamyurek, Hartmut Haeffner

Abstract: High-rate remote entanglement between photon and matter-based qubits is essential for distributed quantum information processing. A key technique to increase the modest entangling rates of existing long-distance quantum networking approaches is multiplexing. Here, we demonstrate a temporally multiplexed ion-photon interface via rapid transport of a chain of nine calcium ions across 74… ▽ More High-rate remote entanglement between photon and matter-based qubits is essential for distributed quantum information processing. A key technique to increase the modest entangling rates of existing long-distance quantum networking approaches is multiplexing. Here, we demonstrate a temporally multiplexed ion-photon interface via rapid transport of a chain of nine calcium ions across 74 $\mathrm{μm}$ within 86 $\mathrm{μs}$. The non-classical nature of the multiplexed photons is verified by measuring the second-order correlation function with an average value of $g^{(2)}(0)$ = 0.060(13), indicating negligible crosstalk between the multiplexed modes. In addition, we characterize the motional degree-of-freedom of the ion crystal after transport and find that it is coherently excited to as much as $\bar{n}_α\approx 110$ for the center-of-mass mode. Our proof-of-principle implementation paves the way for large-scale quantum networking with trapped ions, but highlights some challenges that must be overcome. △ Less

Submitted 7 August, 2026; v1 submitted 16 May, 2024; originally announced May 2024.

Comments: 6 pages, 4 figures

Left-handedness without absorption in the four-level Y-type atomic medium

Authors: Shun-Cai Zhao, Zheng-Dong Liu, Qi-Xuan Wu

Abstract: In this paper,three external fields interacting with the four-level Y-type atomic system described by the density-matrix approach is investigated .The results show that the left-handedness with zero absorption are achieved.And the zero absorption property displays the possibility of manipulation with varying the phase and the intensity of the coupling field. The zero absorption property may be use… ▽ More In this paper,three external fields interacting with the four-level Y-type atomic system described by the density-matrix approach is investigated .The results show that the left-handedness with zero absorption are achieved.And the zero absorption property displays the possibility of manipulation with varying the phase and the intensity of the coupling field. The zero absorption property may be used to amplify the evanescent waves that have been lost in the imaging by traditional lenses.Our scheme proposes an approach to obtain negative refractive medium with zero absorption and the possibility to enhance the imaging resolution in realizing "superlenses". △ Less

Submitted 27 March, 2024; originally announced March 2024.

Comments: 8 pages, 3 figures. arXiv admin note: substantial text overlap with arXiv:2403.00042; text overlap with arXiv:2403.00848

Journal ref: Chin. Phys. B, 19(1): 014211 (2010)

Squeezing below the ground state of motion of a continuously monitored levitating nanoparticle

Authors: Qiongyuan Wu, Diana A. Chisholm, Rafael Muffato, Tiberius Georgescu, Jack Homans, Hendrik Ulbricht, Matteo Carlesso, Mauro Paternostro

Abstract: Squeezing is a crucial resource for quantum information processing and quantum sensing. In levitated nanomechanics, squeezed states of motion can be generated via temporal control of the trapping frequency of a massive particle. However, the amount of achievable squeezing typically suffers from detrimental environmental effects. We analyze the performance of a scheme that, by embedding careful tim… ▽ More Squeezing is a crucial resource for quantum information processing and quantum sensing. In levitated nanomechanics, squeezed states of motion can be generated via temporal control of the trapping frequency of a massive particle. However, the amount of achievable squeezing typically suffers from detrimental environmental effects. We analyze the performance of a scheme that, by embedding careful time-control of trapping potentials and fully accounting for the most relevant sources of noise -- including measurement backaction -- achieves significant levels of mechanical squeezing. The feasibility of our proposal, which is close to experimental state-of-the-art, makes it a valuable tool for quantum state engineering. △ Less

Submitted 19 August, 2024; v1 submitted 27 March, 2024; originally announced March 2024.

Comments: 12 pages, 4 figures, comments are welcome! Quantum Sci. Technol (2024)

Journal ref: Quantum Sci. Technol. 9, 045038 (2024)

2-D isotropic negative refractive index in a N-type four-level atomic system

Authors: Shun-Cai Zhao, Qi-Xuan Wu, Kun Ma

Abstract: 2-D(Two-dimensional) isotropic negative refractive index (NRI) is explicitly realized via the orthogonal signal and coupling standing-wave fields coupling the N-type four-level atomic system. Under some key parameters of the dense vapor media, the atomic system exhibits isotropic NRI with simultaneous negative permittivity and permeability (i.e. Left-handedness) in the 2-D x-y plane. Compared with… ▽ More 2-D(Two-dimensional) isotropic negative refractive index (NRI) is explicitly realized via the orthogonal signal and coupling standing-wave fields coupling the N-type four-level atomic system. Under some key parameters of the dense vapor media, the atomic system exhibits isotropic NRI with simultaneous negative permittivity and permeability (i.e. Left-handedness) in the 2-D x-y plane. Compared with other 2-D NRI schemes, the coherent atomic vapor media in our scheme may be an ideal 2-D isotropic NRI candidate and has some potential advantages, significance or applications in the further investigation. △ Less

Submitted 17 March, 2024; originally announced March 2024.

Comments: 6 pages, 4 figures

Journal ref: Open Phys. 2015; 13:349-354

Effect of Spontaneously Generated Coherence and Detuning on 2D Atom Localization in Two Orthogonal Standing-Wave Fields

Authors: Shun-Cai Zhao, Qi-Xuan Wu, Ai-Ling Gong

Abstract: Two-dimensional (2D) atom localization via the spontaneously generated coherence (SGC) and detunings associated with the probe and standing-wave driving fields in a three-level V-type atomic system are investigated. In the gain process, two equal and tunable peak maxima of position distribution in the plane via the detunings are observed. However, one decreasing and the other increasing peak maxim… ▽ More Two-dimensional (2D) atom localization via the spontaneously generated coherence (SGC) and detunings associated with the probe and standing-wave driving fields in a three-level V-type atomic system are investigated. In the gain process, two equal and tunable peak maxima of position distribution in the plane via the detunings are observed. However, one decreasing and the other increasing peak maxima in the absorption process via the SGC are achieved in the quadrants I and III of the x-y plane. A better resolution and more novelty for the 2D atom localization in our scheme are obtained. △ Less

Submitted 17 March, 2024; originally announced March 2024.

Comments: 8 pages, 5 figures

Journal ref: Chin. Phys. Lett.,31(03): 034206,2014

Left-handedness with three zero-absorption windows tuned by the incoherent pumping field and inter-dot tunnelings in a GaAs/AlGaAs triple quantum dots system

Authors: Shun-Cai Zhao, Shuang-Ying Zhang, Qi-Xuan Wu, Jing Jia

Abstract: Left-handedness with three zero-absorption windows is achieved in a triple-quantum dot (TQD) system. With the typical parameters of a GaAs/AlGaAs heterostructure, the simultaneous negative relative electric permittivity and magnetic permeability are obtained by the adjustable incoherent pumping field and two inter-dot tunnelings. What's more, three zero-absorption windows in the left-handedness fr… ▽ More Left-handedness with three zero-absorption windows is achieved in a triple-quantum dot (TQD) system. With the typical parameters of a GaAs/AlGaAs heterostructure, the simultaneous negative relative electric permittivity and magnetic permeability are obtained by the adjustable incoherent pumping field and two inter-dot tunnelings. What's more, three zero-absorption windows in the left-handedness frequency bands are observed in the TQD system. The left-handedness with zero-absorption in solid state heterostructure may solve not only the challenge in the photonic resonant scheme for left-handed materials (LHMs) but also the application limitation of the negative refractive materials with large amount of absorption. △ Less

Submitted 17 March, 2024; originally announced March 2024.

Comments: 5 pages, 4 figures

Journal ref: Chin. Phys. Lett.,32(5):058104, 2015

Negative refraction without absorption via both coherent and incoherent fields in a four-level left-handed atomic system

Authors: Shun-Cai Zhao, Zheng-Dong Liu, Qi-Xuan Wu

Abstract: This paper attempts a probe into negative refraction without absorption by means of an incoherent pump field and a strong coherent field coupling the dense four-level atomic system.With the application of the incoherent pump field to manipulate the populations in atomic levels and the variable strong coherent field to create quantum coherence, the constraint condition of two equal transition frequ… ▽ More This paper attempts a probe into negative refraction without absorption by means of an incoherent pump field and a strong coherent field coupling the dense four-level atomic system.With the application of the incoherent pump field to manipulate the populations in atomic levels and the variable strong coherent field to create quantum coherence, the constraint condition of two equal transition frequencies responding to the probe field in the atomic system isn't required.And these lead to the propagation transparency and strong magnetic response of the probe field,left-handedness with vanishing absorption in the atomic system.However,an excessive coherent field intensity would increase the absorption. △ Less

Submitted 29 February, 2024; originally announced March 2024.

Comments: 8 pages, 4 figures

Journal ref: Optics Communications, 283 (2010) 3301,3304

Zero absorption and large negative refractive index in a left-handed four-level atomic media

Authors: Shuncai Zhao, Zhengdong Liu, Qixuan Wu

Abstract: In this paper,we have investigated three external fields interacting with the four-level atomic system described by the density-matrix approach.The atomic system exhibits left-handedness with zero absorption as well as large negative refractive index.Varying the parameters of the three external fields,the properties of zero absorption,large negative refractive index from the atomic system keep unv… ▽ More In this paper,we have investigated three external fields interacting with the four-level atomic system described by the density-matrix approach.The atomic system exhibits left-handedness with zero absorption as well as large negative refractive index.Varying the parameters of the three external fields,the properties of zero absorption,large negative refractive index from the atomic system keep unvarying.Our scheme proposes an approach to obtain negative refractive medium with zero absorption. The zero absorption property of atomic system may be used to amplify the evanescent waves that have been lost in the imaging by traditional lenses.And a slab fabricated by the left-handed atomic system may be an ideal candidate for designing perfect lenses. △ Less

Submitted 29 February, 2024; originally announced March 2024.

Comments: 10 pages, 4 figures

Journal ref: J. Phys. B: At. Mol. Opt. Phys. 43 (2010) 045505

Algebraic analysis of electromagnetic chirality-induced negative refractive index in a four-level atomic system

Authors: Shun-Cai Zhao, Qi-Xuan Wu, Ai-Ling Gong

Abstract: This paper presents a algebraic analysis of electromagnetic chirality-induced negative refractive index in a four-level atomic medium. According to analyze mathematically its argument of the complex refractive index for one circular polarization, it found that the negative refractive index without simultaneously negative permittivity and permeability can be obtained when the argument is in the sec… ▽ More This paper presents a algebraic analysis of electromagnetic chirality-induced negative refractive index in a four-level atomic medium. According to analyze mathematically its argument of the complex refractive index for one circular polarization, it found that the negative refractive index without simultaneously negative permittivity and permeability can be obtained when the argument is in the second quadrant of the cartesian coordinate system, and that the probe field coupling to two equal transition frequencies in the atomic level doesn't require. This undoubtedly reduced stringent conditions to negative refractive index by quantum optics. As an application, our scheme may possibly give a novel approach to obtain negative refractive index by electromagnetic chirality-inducing. △ Less

Submitted 13 February, 2024; originally announced February 2024.

Comments: 8 pages, 5 figures

Journal ref: Eur. Phys. J. D, 67:28 (2013)

High quantum yields generated by a multi-band quantum dot photocell

Authors: Shun-Cai Zhao, Qi-Xuan Wu

Abstract: We perform the quantum yields in a multi-band quantum dot (QD) photocell via doping an intermediate band (IB) between the conduction band (CB) and valence band (VB). Under two different sub-band gap layouts, the output power has a prominent enhancement than the single-band gap photocell and the achieved peak photo-to-charge efficiency reaches to 74.9% as compared to the limit efficiency of 63.2% v… ▽ More We perform the quantum yields in a multi-band quantum dot (QD) photocell via doping an intermediate band (IB) between the conduction band (CB) and valence band (VB). Under two different sub-band gap layouts, the output power has a prominent enhancement than the single-band gap photocell and the achieved peak photo-to-charge efficiency reaches to 74.9% as compared to the limit efficiency of 63.2% via the IB approach in the theoretical solar cell prototype. The achieved quantum yields reveal the potential to improve efficiency by some effective theoretical approaches in the QD-IB photocell. △ Less

Submitted 8 February, 2024; originally announced February 2024.

Comments: 9 pages, 3 figures

Journal ref: Superlattices and Microstructures 137 (2020) 106329

Generation of classical non-Gaussian distributions by squeezing a thermal state into non-linear motion of levitated optomechanics

Authors: Rafael Muffato, Tiberius Georgescu, Jack Homans, Thiago Guerreiro, Qiongyuan Wu, Diana Chisholm, Matteo Carlesso, Mauro Paternostro, Hendrik Ulbricht

Abstract: We report on an experiment achieving the dynamical generation of non-Gaussian states of motion of a levitated optomechanical system. We access intrinsic Duffing-like nonlinearities by thermal squeezing of an oscillator's state of motion by rapidly switching the frequency of its trap. We characterize the experimental non-Gaussian state versus expectations from simulations and give prospects for the… ▽ More We report on an experiment achieving the dynamical generation of non-Gaussian states of motion of a levitated optomechanical system. We access intrinsic Duffing-like nonlinearities by thermal squeezing of an oscillator's state of motion by rapidly switching the frequency of its trap. We characterize the experimental non-Gaussian state versus expectations from simulations and give prospects for the emergence of genuine nonclassical features. △ Less

Submitted 24 February, 2025; v1 submitted 8 January, 2024; originally announced January 2024.

Journal ref: Phys. Rev. Research 7, 013171 (2025)

Quantum chaos, integrability, and late times in the Krylov basis

Authors: Vijay Balasubramanian, Javier M. Magan, Qingyue Wu

Abstract: Quantum chaotic systems are conjectured to display a spectrum whose fine-grained features (gaps and correlations) are well described by Random Matrix Theory (RMT). We propose and develop a complementary version of this conjecture: quantum chaotic systems display a Lanczos spectrum whose local means and covariances are well described by RMT. To support this proposal, we first demonstrate its validi… ▽ More Quantum chaotic systems are conjectured to display a spectrum whose fine-grained features (gaps and correlations) are well described by Random Matrix Theory (RMT). We propose and develop a complementary version of this conjecture: quantum chaotic systems display a Lanczos spectrum whose local means and covariances are well described by RMT. To support this proposal, we first demonstrate its validity in examples of chaotic and integrable systems. We then show that for Haar-random initial states in RMTs the mean and covariance of the Lanczos spectrum suffices to produce the full long time behavior of general survival probabilities including the spectral form factor, as well as the spread complexity. In addition, for initial states with continuous overlap with energy eigenstates, we analytically find the long time averages of the probabilities of Krylov basis elements in terms of the mean Lanczos spectrum. This analysis suggests a notion of eigenstate complexity, the statistics of which differentiate integrable systems and classes of quantum chaos. Finally, we clarify the relation between spread complexity and the universality classes of RMT by exploring various values of the Dyson index and Poisson distributed spectra. △ Less

Submitted 6 December, 2023; originally announced December 2023.

A quantum moving target segmentation algorithm for grayscale video

Authors: Wenjie Liu, Lu Wang, Qingshan Wu

Abstract: The moving target segmentation (MTS) aims to segment out moving targets in the video, however, the classical algorithm faces the huge challenge of real-time processing in the current video era. Some scholars have successfully demonstrated the quantum advantages in some video processing tasks, but not concerning moving target segmentation. In this paper, a quantum moving target segmentation algorit… ▽ More The moving target segmentation (MTS) aims to segment out moving targets in the video, however, the classical algorithm faces the huge challenge of real-time processing in the current video era. Some scholars have successfully demonstrated the quantum advantages in some video processing tasks, but not concerning moving target segmentation. In this paper, a quantum moving target segmentation algorithm for grayscale video is proposed, which can use quantum mechanism to simultaneously calculate the difference of all pixels in all adjacent frames and then quickly segment out the moving target. In addition, a feasible quantum comparator is designed to distinguish the grayscale values with the threshold. Then several quantum circuit units, including three-frame difference, binarization and AND operation, are designed in detail, and then are combined together to construct the complete quantum circuits for segmenting the moving target. For a quantum video with $2^m$ frames (every frame is a $2^n\times 2^n$ image with $q$ grayscale levels), the complexity of our algorithm can be reduced to O$(n^2 + q)$. Compared with the classic counterpart, it is an exponential speedup, while its complexity is also superior to the existing quantum algorithms. Finally, the experiment is conducted on IBM Q to show the feasibility of our algorithm in the noisy intermediate-scale quantum (NISQ) era. △ Less

Submitted 1 October, 2023; originally announced October 2023.

Comments: 15 pages, 15 figures

Journal ref: Advanced Quantum Technologies, 2023. 6(12): p.2300248

An optimized quantum minimum searching algorithm with sure-success probability and its experiment simulation with Cirq

Authors: Wenjie Liu, Qingshan Wu, Jiahao Shen, Jiaojiao Zhao, Mohammed Zidan, Lian Tong

Abstract: Finding a minimum is an essential part of mathematical models, and it plays an important role in some optimization problems. Durr and Hoyer proposed a quantum searching algorithm (DHA), with a certain probability of success, to achieve quadratic speed than classical ones. In this paper, we propose an optimized quantum minimum searching algorithm with sure-success probability, which utilizes Grover… ▽ More Finding a minimum is an essential part of mathematical models, and it plays an important role in some optimization problems. Durr and Hoyer proposed a quantum searching algorithm (DHA), with a certain probability of success, to achieve quadratic speed than classical ones. In this paper, we propose an optimized quantum minimum searching algorithm with sure-success probability, which utilizes Grover-Long searching to implement the optimal exact searching, and the dynamic strategy to reduce the iterations of our algorithm. Besides, we optimize the oracle circuit to reduce the number of gates by the simplified rules. The performance evaluation including the theoretical success rate and computational complexity shows that our algorithm has higher accuracy and efficiency than DHA algorithm. Finally, a simulation experiment based on Cirq is performed to verify its feasibility. △ Less

Submitted 25 September, 2023; originally announced September 2023.

Comments: 15 pages, 8 figures. arXiv admin note: text overlap with arXiv:1908.07943 by other authors

Journal ref: Journal of Ambient Intelligence and Humanized Computing,2021.12(11): p.10425-10434

Polarization-based cyclic weak value metrology for angular velocity measurement

Authors: Zi-Rui Zhong, Yue Chen, Wei-Jun Tan, Xiang-Ming Hu, Qing-Lin Wu

Abstract: Weak measurement has been proven to amplify the detection of changes in meters while discarding most photons due to the low probability of post-selection. Previous power-recycling schemes enable the failed post-selection photons to be repeatedly selected, thus overcoming the inefficient post-selection and increasing the precision of detection. In this study, we focus on the polarization-based weak… ▽ More Weak measurement has been proven to amplify the detection of changes in meters while discarding most photons due to the low probability of post-selection. Previous power-recycling schemes enable the failed post-selection photons to be repeatedly selected, thus overcoming the inefficient post-selection and increasing the precision of detection. In this study, we focus on the polarization-based weak value angular-velocity measurement and introduce three cyclic methods to enhance the accuracy of detecting time shift in a Gaussian beam: power recycling, signal recycling, and dual recycling schemes. By incorporating one or two partially transmitting mirrors into the system, both the power and signal-to-noise ratio (SNR) of the detected light are substantially enhanced. Compared to non-polarization schemes, polarization-based approaches offer several advantages, including lower optical loss, unique cyclic directions, and a wider optimal region. These features effectively reduce crosstalk among different light paths and theoretically eliminate the walk-off effect, thus yielding improvements in both theoretical performance and application. △ Less

Submitted 14 March, 2024; v1 submitted 19 September, 2023; originally announced September 2023.

Comments: 9 pages, 4 figures

Dual-recycled interference-based weak value metrology

Authors: Zi-Rui Zhong, Wei-Jun Tan, Yue Chen, Qing-Lin Wu

Abstract: Weak-value-amplification permits small effects to be measured as observable changes at the sacrifice of power due to post-selection. The power recycling scheme has been proven to eliminate this inefficiency of the rare post-selection, thus surpassing the limit of the shot noise and improving the precision of the measurement. However, the improvement is strictly limited by the system setup, especia… ▽ More Weak-value-amplification permits small effects to be measured as observable changes at the sacrifice of power due to post-selection. The power recycling scheme has been proven to eliminate this inefficiency of the rare post-selection, thus surpassing the limit of the shot noise and improving the precision of the measurement. However, the improvement is strictly limited by the system setup, especially the system loss. Here we introduce a dual recycling model based on the interferometric weak-value-based deflection measurement. Two mirrors, the power-recycling mirror and signal-recycling mirror, are placed at the bright and dark port of the interferometer respectively, creating a composite resonator. The results show that both the power and the signal-to-noise ratio (SNR) are greatly enhanced in a wider range of experimental parameters compared to the power-recycling scheme. This work considerably loosens the constraint of the system setup and further explores the real advantage of weak measurement over traditional schemes. △ Less

Submitted 18 September, 2023; v1 submitted 13 September, 2023; originally announced September 2023.

Comments: 7 pages, 5 figures, reference

A Block-Ring connected Topology of Parameterized Quantum Circuits

Authors: Wenjie Liu, Qingshan Wu

Abstract: It is essential to select efficient topology of parameterized quantum circuits (PQCs) in variational quantum algorithms (VQAs). However, there are problems in current circuits, i.e. optimization difficulties caused by too many parameters or performance is hard to guarantee. How to reduce the number of parameters (number of single-qubit rotation gates and 2-qubit gates) in PQCs without reducing the… ▽ More It is essential to select efficient topology of parameterized quantum circuits (PQCs) in variational quantum algorithms (VQAs). However, there are problems in current circuits, i.e. optimization difficulties caused by too many parameters or performance is hard to guarantee. How to reduce the number of parameters (number of single-qubit rotation gates and 2-qubit gates) in PQCs without reducing the performance has become a new challenge. To solve this problem, we propose a novel topology, called Block-Ring (BR) topology, to construct the PQCs. This topology allocate all qubits to several blocks, all-to-all mode is adopt inside each block and ring mode is applied to connect different blocks. Compared with the pure all-to-all topology circuits which own the best power, BR topology have similar performance and the number of parameters and 2-qubit gate reduced from 0(n^2) to 0(mn) , m is a hyperparameter set by ourselves. Besides, we compared BR topology with other topology circuits in terms of expressibility and entangling capability. Considering the effects of different 2-qubit gates on circuits, we also make a distinction between controlled X-rotation gates and controlled Z-rotation gates. Finally, the 1- and 2-layer configurations of PQCs are taken into consideration as well, which shows the BR's performance improvement in the condition of multilayer circuits. △ Less

Submitted 21 August, 2023; originally announced August 2023.

Comments: 9 pages, 12 figures

Qubits on programmable geometries with a trapped-ion quantum processor

Authors: Qiming Wu, Yue Shi, Jiehang Zhang

Abstract: Geometry and dimensionality have played crucial roles in our understanding of the fundamental laws of nature, with examples ranging from curved space-time in general relativity to modern theories of quantum gravity. In quantum many-body systems, the entanglement structure can change if the constituents are connected differently, leading to altered bounds for correlation growth and difficulties for… ▽ More Geometry and dimensionality have played crucial roles in our understanding of the fundamental laws of nature, with examples ranging from curved space-time in general relativity to modern theories of quantum gravity. In quantum many-body systems, the entanglement structure can change if the constituents are connected differently, leading to altered bounds for correlation growth and difficulties for classical computers to simulate large systems. While a universal quantum computer can perform digital simulations, an analog-digital hybrid quantum processor offers advantages such as parallelism. Here, we engineer a class of high-dimensional Ising interactions using a linear one-dimensional (1D) ion chain with up to 8 qubits through stroboscopic sequences of commuting Hamiltonians. %with a thorough understanding of the error sources and deviation from the target Hamiltonian. In addition, we extend this method to non-commuting circuits and demonstrate the quantum XY and Heisenberg models using Floquet periodic drives with tunable symmetries. The realization of higher dimensional spin models offers new opportunities ranging from studying topological phases of matter or quantum spin glasses to future fault-tolerant quantum computation. △ Less

Submitted 20 August, 2023; originally announced August 2023.

Comments: 6 pages, 4 figures

Bloch-Wave Interferometry of Driven Quasiparticles in Bulk GaAs

Authors: Seamus D. O'Hara, Joseph B. Costello, Qile Wu, Ken West, Loren Pfeiffer, Mark S. Sherwin

Abstract: We report that the polarizations of sidebands emitted from bulk gallium arsenide (GaAs) driven by a strong terahertz (THz) laser while probed with a weak near-infrared laser can be viewed as interferograms from a Michelson-like interferometer for Bloch waves. A simple analytical model is introduced to calculate the difference in quantum mechanical phases accumulated by Bloch waves associated with… ▽ More We report that the polarizations of sidebands emitted from bulk gallium arsenide (GaAs) driven by a strong terahertz (THz) laser while probed with a weak near-infrared laser can be viewed as interferograms from a Michelson-like interferometer for Bloch waves. A simple analytical model is introduced to calculate the difference in quantum mechanical phases accumulated by Bloch waves associated with electron-heavy hole and electron-light hole pairs in their respective interferometer arms. The measured and calculated spectra are in good quantitative agreement, including scaling with THz field strength. Our results indicate a simple way to extract material parameters in future experiments △ Less

Submitted 20 May, 2023; originally announced May 2023.

Experimentally demonstrating indefinite causal order algorithms to solve the generalized Deutsch's problem

Authors: Wen-Qiang Liu, Zhe Meng, Bo-Wen Song, Jian Li, Qing-Yuan Wu, Xiao-Xiao Chen, Jin-Yang Hong, An-Ning Zhang, Zhang-qi Yin

Abstract: Deutsch's algorithm is the first quantum algorithm to show the advantage over the classical algorithm. Here we generalize Deutsch's problem to $n$ functions and propose a new quantum algorithm with indefinite causal order to solve this problem. The new algorithm not only reduces the number of queries to the black-box by half over the classical algorithm, but also significantly reduces the number o… ▽ More Deutsch's algorithm is the first quantum algorithm to show the advantage over the classical algorithm. Here we generalize Deutsch's problem to $n$ functions and propose a new quantum algorithm with indefinite causal order to solve this problem. The new algorithm not only reduces the number of queries to the black-box by half over the classical algorithm, but also significantly reduces the number of required quantum gates over the Deutsch's algorithm. We experimentally demonstrate the algorithm in a stable Sagnac loop interferometer with common path, which overcomes the obstacles of both phase instability and low fidelity of Mach-Zehnder interferometer. The experimental results have shown both an ultra-high and robust success probability $\sim 99.7\%$. Our work opens up a new path towards solving the practical problems with indefinite casual order quantum circuits. △ Less

Submitted 9 May, 2023; v1 submitted 9 May, 2023; originally announced May 2023.

Journal ref: Advanced Quantum Technologies 7, 2400181 (2024)

Non-equilibrium quantum thermodynamics of a particle trapped in a controllable time-varying potential

Authors: Qiongyuan Wu, Matteo Carlesso

Abstract: Non-equilibrium thermodynamics can provide strong advantages when compared to more standard equilibrium situations. Here, we present a general framework to study its application to concrete problems, which is valid also beyond the assumption of a Gaussian dynamics. We consider two different problems: 1) the dynamics of a levitated nanoparticle undergoing the transition from an harmonic to a double… ▽ More Non-equilibrium thermodynamics can provide strong advantages when compared to more standard equilibrium situations. Here, we present a general framework to study its application to concrete problems, which is valid also beyond the assumption of a Gaussian dynamics. We consider two different problems: 1) the dynamics of a levitated nanoparticle undergoing the transition from an harmonic to a double-well potential; 2) the transfer of a quantum state across a double-well potential through classical and quantum protocols. In both cases, we assume that the system undergoes to decoherence and thermalisation. In case 1), we construct a numerical approach to the problem and study the non-equilibrium thermodynamics of the system. In case 2), we introduce a new figure of merit to quantify the efficiency of a state-transfer protocol and apply it to quantum and classical versions of such protocols. △ Less

Submitted 14 March, 2023; v1 submitted 9 March, 2023; originally announced March 2023.

Journal ref: Proc. SPIE 12447, Quantum Sensing, Imaging, and Precision Metrology, 1244714 (8 March 2023)

Extension of Noether's theorem in PT-symmetric systems and its experimental demonstration in an optical setup

Authors: Q. C. Wu, J. L. Zhao, Y. L. Fang, Y. Zhang, D. X. Chen, C. P. Yang, F. Nori

Abstract: Noether's theorem is one of the fundamental laws in physics, relating the symmetry of a physical system to its constant of motion and conservation law. On the other hand, there exist a variety of non-Hermitian parity-time (PT)-symmetric systems, which exhibit novel quantum properties and have attracted increasing interest. In this work, we extend Noether's theorem to a class of significant PT -sym… ▽ More Noether's theorem is one of the fundamental laws in physics, relating the symmetry of a physical system to its constant of motion and conservation law. On the other hand, there exist a variety of non-Hermitian parity-time (PT)-symmetric systems, which exhibit novel quantum properties and have attracted increasing interest. In this work, we extend Noether's theorem to a class of significant PT -symmetric systems for which the eigenvalues of the PT-symmetric Hamiltonian H change from purely real numbers to purely imaginary numbers,and introduce a generalized expectation value of an operator based on biorthogonal quantum mechanics. We find that the generalized expectation value of a time-independent operator is a constant of motion when the operator presents a standard symmetry in the PT -symmetry unbroken regime, or a chiral symmetry in the PT-symmetry broken regime. In addition, we experimentally investigate the extended Noether's theorem in PT -symmetric single-qubit and two-qubit systems using an optical setup. Our experiment demonstrates the existence of the constant of motion and reveals how this constant of motion can be used to judge whether the PT -symmetry of a system is broken. Furthermore, a novel phenomenon of masking quantum information is first observed in a PT -symmetric two-qubit system. This study not only contributes to full understanding of the relation between symmetry and conservation law in PT -symmetric physics, but also has potential applications in quantum information theory and quantum communication protocols. △ Less

Submitted 8 February, 2023; v1 submitted 18 January, 2023; originally announced January 2023.

Comments: 12 pages, 4 figures

Journal ref: Sci. China-Phys. Mech. Astron. 66, 240311 (2023)

$n$-photon blockade with an $n$-photon parametric drive

Authors: Yan-Hui Zhou, Fabrizio Minganti, Wei Qin, Qi-Cheng Wu, Junlong Zhao, Yu-Liang Fang, Franco Nori, Chui-Ping Yang

Abstract: We propose a mechanism to engineer an $n$-photon blockade in a nonlinear cavity with an $n$-photon parametric drive $λ(\hat{a}^{†n}+\hat{a}^n)$. When an $n$-photon-excitation resonance condition is satisfied, the presence of n photons in the cavity suppresses the absorption of the subsequent photons. To confirm the validity of this proposal, we study the n-photon blockade in an atom-cavity system,… ▽ More We propose a mechanism to engineer an $n$-photon blockade in a nonlinear cavity with an $n$-photon parametric drive $λ(\hat{a}^{†n}+\hat{a}^n)$. When an $n$-photon-excitation resonance condition is satisfied, the presence of n photons in the cavity suppresses the absorption of the subsequent photons. To confirm the validity of this proposal, we study the n-photon blockade in an atom-cavity system, a Kerr-nonlinear resonator, and two-coupled Kerr nonlinear resonators. Our results demonstrate that $n$-photon bunching and $(n+1)$-photon antibunching can be simultaneously obtained in these systems. This effect is due both to the anharmonic energy ladder and to the nature of the $n$-photon drive. To show the importance of the drive, we compare the results of the $n$-photon drive with a coherent (one-photon) drive, proving the enhancement of antibunching in the parametric-drive case. This proposal is general and can be applied to realize the $n$-photon blockade in other nonlinear systems. △ Less

Submitted 7 January, 2023; originally announced January 2023.

Journal ref: Physical Review A 104, 053718 (2021)