Showing 1–23 of 23 results for author: Qin, Y

Experimental realization of the complete seven-phase Anderson-localization landscape

Authors: Yao Qin, Chao Yang, Yuzhe Zhang, Yucheng Wang, Jingyun Fan

Abstract: Anderson localization has evolved far beyond the conventional dichotomy between extended and localized states. Modern localization theory predicts a complete transport hierarchy comprising extended, critical, and localized phases together with all coexistence phases among them, forming a seven-phase Anderson-localization landscape. Despite its fundamental importance, this hierarchy has never been… ▽ More Anderson localization has evolved far beyond the conventional dichotomy between extended and localized states. Modern localization theory predicts a complete transport hierarchy comprising extended, critical, and localized phases together with all coexistence phases among them, forming a seven-phase Anderson-localization landscape. Despite its fundamental importance, this hierarchy has never been experimentally realized within a single system. Here we realize the complete seven-phase Anderson-localization landscape in a one-dimensional Floquet photonic lattice. By engineering quasiperiodic hopping profiles containing inhomogeneously distributed hopping zeros, we generate critical states and enable their coexistence with extended and localized sectors. The resulting transport regimes are directly resolved through their distinct spatiotemporal dynamics, including ballistic expansion, confined critical oscillations, and persistent localization. We observe all seven phases, including the elusive triply coexisting extended-critical-localized phase, and experimentally track the phase transitions connecting them. Our results establish the first complete experimental map of the Anderson-localization landscape and provide a unified platform for investigating mobility edges, multifractality, and programmable coherent transport. △ Less

Submitted 21 June, 2026; v1 submitted 12 June, 2026; originally announced June 2026.

Drag-induced skin effect in a Bose-Fermi mixture

Authors: Wenjie Liu, Ching Hua Lee, Yi Qin

Abstract: The non-Hermitian skin effect (NHSE) represents one of the most distinctive phenomena in non-Hermitian physics. Here, we uncover a new drag-induced NHSE mechanism in interacting Bose--Fermi mixtures where only bosons and not fermions experience asymmetric hoppings. %While bosons exhibit intrinsic skin localization due to asymmetric hopping, fermions remain Hermitian in isolation and do not indepen… ▽ More The non-Hermitian skin effect (NHSE) represents one of the most distinctive phenomena in non-Hermitian physics. Here, we uncover a new drag-induced NHSE mechanism in interacting Bose--Fermi mixtures where only bosons and not fermions experience asymmetric hoppings. %While bosons exhibit intrinsic skin localization due to asymmetric hopping, fermions remain Hermitian in isolation and do not independently support NHSE. We show that strong Bose--Fermi interactions enable fermions to inherit boundary accumulation through correlated bound states. %In the few-body regime, The interplay of interactions, quantum statistics, and non-Hermitian dynamics gives rise to an interaction-induced blockade mechanism, leading to highly asymmetric fermionic transport. We demonstrate that the drag-induced NHSE is dynamically stable and propose a feasible realization in ultracold Bose--Fermi mixtures with Floquet-engineered asymmetric tunneling. Our results establish a general interaction-mediated mechanism for emergent non-Hermitian localization in hybrid quantum matter. △ Less

Submitted 2 June, 2026; originally announced June 2026.

Anyon-Induced Criticality and Dynamical Stability in Non-Hermitian Many-Body Systems

Authors: Yi Qin, Yee Sin Ang, Linhu Li, Ching Hua Lee

Abstract: We show that anyonic statistics fundamentally reshapes non-Hermitian many-body physics by intrinsically breaking pseudo-Hermiticity, leading to a unique real-complex spectral transition with characteristically dense states in Im$E$. This anyon-induced transition occurs even when bosonic and pseudofermionic counterparts remain entirely real, revealing a form of non-Hermitian criticality driven pure… ▽ More We show that anyonic statistics fundamentally reshapes non-Hermitian many-body physics by intrinsically breaking pseudo-Hermiticity, leading to a unique real-complex spectral transition with characteristically dense states in Im$E$. This anyon-induced transition occurs even when bosonic and pseudofermionic counterparts remain entirely real, revealing a form of non-Hermitian criticality driven purely by exchange statistics. The resulting spectrum exhibits enhanced gaps in Im$E$ that dynamically isolate dominant eigenstates, producing anomalously stable short-time quench dynamics for anyons. Our results identify anyonic statistics as an intrinsic mechanism for generating unconventional non-Hermitian critical behavior usually associated with highly non-local systems. △ Less

Submitted 18 March, 2026; originally announced March 2026.

Comments: 19 pages, 12 figures

Many-body critical non-Hermitian skin effect

Authors: Yi Qin, Yee Sin Ang, Ching Hua Lee, Linhu Li

Abstract: Criticality in non-Hermitian systems unveils unique phase transitions and scaling behaviors beyond Hermitian paradigms, offering new insights into the interplay between gain/loss, non-reciprocity, and complex energy spectra. In this paper, we uncover a new class of many-body critical non-Hermitian skin effect (CSE) originating from the interplay between multiple non-Hermitian pumping channels and… ▽ More Criticality in non-Hermitian systems unveils unique phase transitions and scaling behaviors beyond Hermitian paradigms, offering new insights into the interplay between gain/loss, non-reciprocity, and complex energy spectra. In this paper, we uncover a new class of many-body critical non-Hermitian skin effect (CSE) originating from the interplay between multiple non-Hermitian pumping channels and Hubbard interactions. In particular, criticality in the real-to-complex transitions can selectively emerge within the subspace of bound states or scattering states, as well as their interacting admixtures. These mechanisms possess no single-particle analog and can be diagnosed through a specially defined correlation function. As more particles are involved, higher-order CSEs naturally arise, with greatly enhanced effective coupling strengths and hence greater experimental accessibility. Our results reveal an enriched landscape of non-Hermitian critical phenomena in interacting many-body systems, and pave the way for investigating unconventional non-Hermitian criticality in the context of various interaction-induced particle clustering configurations. △ Less

Submitted 2 June, 2025; originally announced June 2025.

Comments: 16 pages, 12 figures

Journal ref: Communications Physics 9, 16 (2026)

Hybrid and scalable photonic circuit cavity quantum electrodynamics

Authors: Xudong Wang, Yifan Zhu, Xiuqi Zhang, Yuanhao Qin, Bowen Chen, Yang Chen, Yongheng Huo, Jiaxiang Zhang, Xin Ou

Abstract: Similar to superconducting circuit quantum electrodynamics (cQED), the development of a photonic analog--specifically, photonic circuit cQED--has become a major focus in integrated quantum photonics. Current solid-state cQED devices, however, face scalability challenges due to the difficulty in simultaneously spectral tuning of cavity modes and quantum emitters while ensuring in-plane optical mode… ▽ More Similar to superconducting circuit quantum electrodynamics (cQED), the development of a photonic analog--specifically, photonic circuit cQED--has become a major focus in integrated quantum photonics. Current solid-state cQED devices, however, face scalability challenges due to the difficulty in simultaneously spectral tuning of cavity modes and quantum emitters while ensuring in-plane optical modes confinement for efficient on-chip light routing. Here, we overcome these limitations by proposing and demonstrating a hybrid solid-state cQED platform integrated on a chip. Our device integrates semiconducting quantum dots (QDs) with a thin-film lithium niobate (TFLN) microring resonator. Leveraging TFLN's ferroelectric and electro-optic (EO) properties, we implement local spectral tuning of both waveguide-coupled QDs and cavity modes. This approach achieves a broad spectral tuning range of up to 4.82 nm for individual QDs, enabling deterministic on-chip single-photon emission with a Purcell factor of 3.52. When combined with EO cavity tuning, we realize a spectrally tunable hybrid photonic circuit cQED device, sustaining near-constant Purcell factors of 1.89 over a 0.30 nm spectral range. This achievement enables scalable on-chip cavity-enhanced single-photon sources while preserving optical properties and maintaining compatibility with advanced photonic architectures, marking a significant step toward practical implementation of large-scale chip-based quantum networks. △ Less

Submitted 6 April, 2025; originally announced April 2025.

Large-scale quantum-dot-lithium-niobate hybrid integrated photonic circuits enabling on-chip quantum networking

Authors: Xudong Wang, Xiuqi Zhang, Bowen Chen, Yifan Zhu, Yuanhao Qin, Lvbin Dong, Jiachen Cai, Dongchen Sui, Jinbo Wu, Quan Zhang

Abstract: Hybrid integrated quantum photonics combines solid-state artificial atoms with reconfigurable photonic circuits, enabling scalable chip-based quantum networks. Self-assembled quantum dots (QDs) are ideal for this goal due to their ability to generate highly indistinguishable single photons with exceptional brightness. Integrating QDs into low-loss photonic circuits can facilitate complex quantum n… ▽ More Hybrid integrated quantum photonics combines solid-state artificial atoms with reconfigurable photonic circuits, enabling scalable chip-based quantum networks. Self-assembled quantum dots (QDs) are ideal for this goal due to their ability to generate highly indistinguishable single photons with exceptional brightness. Integrating QDs into low-loss photonic circuits can facilitate complex quantum networks by enabling entanglement transfer via two-photon interference. However, challenges such as limited scalability, spectral inhomogeneity, and quantum interference between independent sources remain. We present a hybrid photonic architecture that integrates QD-containing waveguides with low-loss lithium niobate (LN) circuits, incorporating 20 deterministic single-photon sources (SPSs). Using the piezoelectric properties of thin-film lithium niobate (TFLN), we achieve on-chip local spectral tuning of QD emissions by up to 7.7 meV,three orders of magnitude greater than the transform-limited linewidth. This approach enables on-chip quantum interference with a visibility of 0.73 between two spatially separated QD SPSs connected by 0.48 mm long waveguides, establishing a functional quantum network.The large-scale integration of spectrally tunable QD-based SPSs into low-loss LN circuits, combined with fast electro-optical switching, paves the way for compact, lightweight, and scalable photonic quantum networks. △ Less

Submitted 31 March, 2025; originally announced March 2025.

A hybrid single quantum dot coupled cavity on a CMOS-compatible SiC photonic chip for Purcell-enhanced deterministic single-photon emission

Authors: Yifan Zhu, Runze Liu, Ailun Yi, Xudong Wang, Yuanhao Qin, Zihao Zhao, Junyi Zhao, Bowen Chen, Xiuqi Zhang, Sannian Song, Yongheng Huo, Xin Ou, Jiaxiang Zhang

Abstract: The ability to control nonclassical light emission from a single quantum emitter by an integrated cavity may unleash new perspectives for integrated photonic quantum applications. However, coupling a single quantum emitter to cavity within photonic circuitry towards creation of the Purcell-enhanced single-photon emission is elusive due to the complexity of integrating active devices in low-loss ph… ▽ More The ability to control nonclassical light emission from a single quantum emitter by an integrated cavity may unleash new perspectives for integrated photonic quantum applications. However, coupling a single quantum emitter to cavity within photonic circuitry towards creation of the Purcell-enhanced single-photon emission is elusive due to the complexity of integrating active devices in low-loss photonic circuits. Here we demonstrate a hybrid micro-ring resonator (HMRR) coupled with self-assembled quantum dots (QDs) for cavity-enhanced deterministic single-photon emission. The HMRR cavity supports whispering-gallery modes with quality factors up to 7800. By further introducing a micro-heater, we show that the photon emission of QDs can be locally and dynamically tuned over one free spectral ranges of the HMRR (~4 nm). This allows precise tuning of individual QDs in resonance with the cavity modes, thereby enhancing single-photon emission with a Purcell factor of about 4.9. Our results on the hybrid integrated cavities coupled with two-level quantum emitters emerge as promising devices for chip-based scalable photonic quantum applications. △ Less

Submitted 10 November, 2024; originally announced November 2024.

Dynamical suppression of many-body non-Hermitian skin effect in Anyonic systems

Authors: Yi Qin, Ching Hua Lee, Linhu Li

Abstract: The non-Hermitian skin effect (NHSE) is a fascinating phenomenon in nonequilibrium systems where eigenstates massively localize at the systems' boundaries, pumping (quasi-)particles loaded in these systems unidirectionally to the boundaries. Its interplay with many-body effects have been vigorously studied recently, and inter-particle repulsion or Fermi degeneracy pressure have been shown to limit… ▽ More The non-Hermitian skin effect (NHSE) is a fascinating phenomenon in nonequilibrium systems where eigenstates massively localize at the systems' boundaries, pumping (quasi-)particles loaded in these systems unidirectionally to the boundaries. Its interplay with many-body effects have been vigorously studied recently, and inter-particle repulsion or Fermi degeneracy pressure have been shown to limit the boundary accumulation induced by the NHSE both in their eigensolutions and dynamics. However, in this work we found that anyonic statistics can even more profoundly affect the NHSE dynamics, suppressing or even reversing the state dynamicss against the localizing direction of the NHSE. This phenomenon is found to be more pronounced when more particles are involved.The spreading of quantum information in this system shows even more exotic phenomena, where NHSE affects only the information dynamics for a thermal ensemble, but not that for a single initial state. Our results open up a new avenue on exploring novel non-Hermitian phenomena arisen from the interplay between NHSE and anyonic statistics, and can potentially be demonstrated in ultracold atomic quantum simulators and quantum computers. △ Less

Submitted 26 November, 2024; v1 submitted 20 May, 2024; originally announced May 2024.

Comments: 17 pages, 15 figures

Journal ref: Commun Phys 8, 18 (2025)

Enhanced quantum sensing with amplification and deamplification

Authors: Min Jiang, Yushu Qin, Yuanhong Wang, Ying Huang, Xinhua Peng, Dmitry Budker

Abstract: Quantum sensing is a fundamental building block of modern technology that employs quantum resources and creates new opportunities for precision measurements. However, previous methods usually have a common assumption that detection noise levels should be below the intrinsic sensitivity provided by quantum resources. Here we report the first demonstration of Fano resonance between coupled alkali-me… ▽ More Quantum sensing is a fundamental building block of modern technology that employs quantum resources and creates new opportunities for precision measurements. However, previous methods usually have a common assumption that detection noise levels should be below the intrinsic sensitivity provided by quantum resources. Here we report the first demonstration of Fano resonance between coupled alkali-metal and noble gases through rapid spin-exchange collisions. The Fano resonance gives rise to two intriguing phenomena: spin amplification and deamplification, which serve as crucial resources for enhanced sensing. Further we develop a novel scheme of quantum sensing enhanced by amplification and deamplification, with relaxed requirements on the detection noise. The coupled systems of alkali-metal and noble gases act as amplifiers or de-amplifiers, enabling to extract small signals above the detection noise before final detection. We demonstrate magnetic-field measurement about 54 decibels below the photon-shot noise, which outperforms the state-of-the-art squeezed-light technology and realizes femtotesla-level sensitivity. Our work opens new avenues to applications in searches for ultralight dark matter with sensitivity well beyond the supernova-observation constraints. △ Less

Submitted 31 August, 2023; originally announced September 2023.

Comments: 7 pages, 4 figures

Occupation-dependent particle separation in one-dimensional non-Hermitian lattices

Authors: Yi Qin, Linhu Li

Abstract: We unveil an exotic phenomenon arising from the intricate interplay between non-Hermiticity and many-body physics, namely an occupation-dependent particle separation for hardcore bosons in a one-dimensional lattice driven by uni-directional non-Hermitian pumping. Taking hardcore bosons as an example, we find that a pair of particles occupying the same unit cell exhibit an opposite non-Hermitian pu… ▽ More We unveil an exotic phenomenon arising from the intricate interplay between non-Hermiticity and many-body physics, namely an occupation-dependent particle separation for hardcore bosons in a one-dimensional lattice driven by uni-directional non-Hermitian pumping. Taking hardcore bosons as an example, we find that a pair of particles occupying the same unit cell exhibit an opposite non-Hermitian pumping direction to that of unpaired ones occupying different unit cells. By turning on an intracell interaction, many-body eigenstates split in their real energies, forming separable clusters in the complex energy plane with either left-, right-, or bipolar-types of non-Hermitian skin effect (NHSE). The dependency of skin accumulating directions on particle occupation is further justified with local sublattice correlation and entanglement entropy of many-body eigenstates. Dynamically, this occupation-dependent NHSE manifests as uni- or bi-directional pumping for many-body initial states, allowing for spatially separating paired and unpaired particles. Similar phenomena also apply to fermionic systems, unveiling the possibility of designing and exploring novel non-Hermitian phases originated from particle non-conservation in subsystems (e.g., orbitals, sublattices, or spin species) and their spatial configurations. △ Less

Submitted 28 July, 2023; v1 submitted 16 July, 2023; originally announced July 2023.

Comments: 18pages, 14 fiugres

Journal ref: Phys. Rev. Lett. 132, 096501 (2024)

Strain Anisotropy Driven Spontaneous Formation of Nanoscrolls from Two-Dimensional Janus Layers

Authors: Mohammed Sayyad, Ying Qin, Jan Kopaczek, Adway Gupta, Naim Patoary, Shantanu Sinha, Emmie Benard, Austin Davis, Kentaro Yumigeta, Cheng-Lun Wu, Han Li, Shize Yang, Ivan Sanchez Esqueda, Arunima Singh, Sefaattin Tongay

Abstract: Two-dimensional Janus transition metal dichalcogenides (TMDs) have attracted attention due to their emergent properties arising from broken mirror symmetry and self-driven polarisation fields. While it has been proposed that their vdW superlattices hold the key to achieving superior properties in piezoelectricity and photovoltiacs, available synthesis has ultimately limited their realisation. Here… ▽ More Two-dimensional Janus transition metal dichalcogenides (TMDs) have attracted attention due to their emergent properties arising from broken mirror symmetry and self-driven polarisation fields. While it has been proposed that their vdW superlattices hold the key to achieving superior properties in piezoelectricity and photovoltiacs, available synthesis has ultimately limited their realisation. Here, we report the first packed vdW nanoscrolls made from Janus TMDs through a simple one-drop solution technique. Our results, including ab-initio simulations, show that the Bohr radius difference between the top sulphur and the bottom selenium atoms within Janus M_Se^S (M=Mo, W) results in a permanent compressive surface strain that acts as a nanoscroll formation catalyst after small liquid interaction. Unlike classical 2D layers, the surface strain in Janus TMDs can be engineered from compressive to tensile by placing larger Bohr radius atoms on top (M_S^Se) to yield inverted C scrolls. Detailed microscopy studies offer the first insights into their morphology and readily formed Moiré lattices. In contrast, spectroscopy and FETs studies establish their excitonic and device properties and highlight significant differences compared to 2D flat Janus TMDs. These results introduce the first polar Janus TMD nanoscrolls and introduce inherent strain-driven scrolling dynamics as a catalyst to create superlattices. △ Less

Submitted 31 May, 2023; originally announced June 2023.

Geometry-dependent skin effect and anisotropic Bloch oscillations in a non-Hermitian optical lattice

Authors: Yi Qin, Kai Zhang, Linhu Li

Abstract: The interplay between the non-Hermiticity and dimensionality gives rise to exotic characteristics in higher dimensions, with one representative phenomenon known as the geometry-dependent skin effect (GDSE), which refers to that the localization of extensive eigenstates depends on the system's geometry under open boundary conditions. In this paper, we demonstrate the emergence of GDSE in a two-dime… ▽ More The interplay between the non-Hermiticity and dimensionality gives rise to exotic characteristics in higher dimensions, with one representative phenomenon known as the geometry-dependent skin effect (GDSE), which refers to that the localization of extensive eigenstates depends on the system's geometry under open boundary conditions. In this paper, we demonstrate the emergence of GDSE in a two-dimensional $sp$ optical ladder lattice with on-site atom loss, which can be manifested by anisotropic dynamics of Bloch oscillations in the bulk of the system. By applying a static force in different directions, the wave-packet dynamics retrieve the complex energy spectra with either nonzero or zero spectral winding number, indicating the presence or absence of skin accumulation in the corresponding directions, respectively. Our results reveal that the GDSE has an intrinsic anisotropic bulk dynamics independent of boundary conditions, and offer its realization and detection in quantum systems. △ Less

Submitted 7 April, 2023; originally announced April 2023.

Comments: 16 pages, 13 figures

Journal ref: Phys. Rev. A 109, 023317 (2024)

The optical rogue wave patterns in coupled defocusing systems

Authors: Yan-Hong Qin, Liming Ling, Li-Chen Zhao

Abstract: We systematically investigate rogue wave's spatial-temporal pattern in $N$ $(N\geq2)$-component coupled defocusing nonlinear Schrödinger equations. The fundamental rogue wave solutions are given in a unified form for both focusing and defocusing cases. We establish the quantitative correspondence between modulation instability and rogue wave patterns, which develops the previously reported inequal… ▽ More We systematically investigate rogue wave's spatial-temporal pattern in $N$ $(N\geq2)$-component coupled defocusing nonlinear Schrödinger equations. The fundamental rogue wave solutions are given in a unified form for both focusing and defocusing cases. We establish the quantitative correspondence between modulation instability and rogue wave patterns, which develops the previously reported inequality relation into an equation correspondence. As an example, we demonstrate phase diagrams for rogue wave patterns in a two-component coupled system, based on the complete classification of their spatial-temporal structures. The phase diagrams enable us to predict various rogue wave patterns, such as the ones with a four-petaled structure in both components. These results are meaningful for controlling the rogue wave excitations in two orthogonal polarization optical fibers. △ Less

Submitted 15 December, 2022; originally announced December 2022.

Comments: 6 pages,2 figures

SAPPHIRE: Search for exotic parity-violation interactions with quantum spin amplifiers

Authors: Yuanhong Wang, Ying Huang, Chang Guo, Min Jiang, Xiang Kang, Haowen Su, Yushu Qin, Wei Ji, Dongdong Hu, Xinhua Peng, Dmitry Budker

Abstract: Quantum sensing provides sensitive tabletop tools to search for exotic spin-dependent interactions beyond the Standard Model, which has attracted great attention in theories and experiments. Here we develop a technique based on quantum Spin Amplifier for Particle PHysIcs REsearch (SAPPHIRE) to resonantly search for exotic interactions, specifically parity-odd spin-spin interactions. The present te… ▽ More Quantum sensing provides sensitive tabletop tools to search for exotic spin-dependent interactions beyond the Standard Model, which has attracted great attention in theories and experiments. Here we develop a technique based on quantum Spin Amplifier for Particle PHysIcs REsearch (SAPPHIRE) to resonantly search for exotic interactions, specifically parity-odd spin-spin interactions. The present technique effectively amplifies the pseudomagnetic field generated by exotic interactions by a factor of about 200 while being insensitive to spurious external magnetic fields. Our studies, using such a quantum amplification technique, open the doors to exploring the parity-violation interactions mediated by Z' bosons in the challenging parameter space (force range between 3 mm and 0.1 km) and set the most stringent constraints on Z'-mediated electron-neutron couplings, significantly improving previous limits by up to five orders of magnitude. Moreover, our bounds on Z'-mediated couplings between nucleons reaches into a hitherto unexplored parameter space (force range below 1 m), complementing the existing astrophysical and laboratory studies. △ Less

Submitted 15 May, 2022; originally announced May 2022.

Comments: 8 pages, 5 figures

Journal ref: Science advances. 2023 Jan 6;9(1):eade0353

Floquet Spin Amplification

Authors: Min Jiang, Yushu Qin, Xin Wang, Yuanhong Wang, Haowen Su, Xinhua Peng, Dmitry Budker

Abstract: Detection of weak electromagnetic waves and hypothetical particles aided by quantum amplification is important for fundamental physics and applications. However, demonstrations of quantum amplification are still limited; in particular, the physics of quantum amplification is not fully explored in periodically driven (Floquet) systems, which are generally defined by time-periodic Hamiltonians and e… ▽ More Detection of weak electromagnetic waves and hypothetical particles aided by quantum amplification is important for fundamental physics and applications. However, demonstrations of quantum amplification are still limited; in particular, the physics of quantum amplification is not fully explored in periodically driven (Floquet) systems, which are generally defined by time-periodic Hamiltonians and enable observation of many exotic quantum phenomena such as time crystals. Here we investigate the magnetic-field signal amplification by periodically driven $^{129}$Xe spins and observe signal amplification at frequencies of transitions between Floquet spin states. This "Floquet amplification" allows to simultaneously enhance and measure multiple magnetic fields with at least one order of magnitude improvement, offering the capability of femtotesla-level measurements. Our findings extend the physics of quantum amplification to Floquet systems and can be generalized to a wide variety of existing amplifiers, enabling a previously unexplored class of "Floquet amplifiers". △ Less

Submitted 12 December, 2021; originally announced December 2021.

Comments: 6 pages

Enhancement of spin noise spectroscopy of rubidium atomic ensemble by using of the polarization squeezed light

Authors: Lele Bai, Lulu Zhang, Yongbiao Yang, Rui Chang, Yao Qin, Jun He, Xin Wen, Junmin Wang

Abstract: We measured the spin noise spectroscopy (SNS) of rubidium atomic ensemble with two different atomic vapor cells (filled with the buffer gases or coated with paraffin film on the inner wall), and demonstrated the enhancement of signal to noise ratio (SNR) by using of the polarization squeezed state (PSS) of 795 nm light field with Stokes operator S2 squeezed. PSS is prepared by locking the relative… ▽ More We measured the spin noise spectroscopy (SNS) of rubidium atomic ensemble with two different atomic vapor cells (filled with the buffer gases or coated with paraffin film on the inner wall), and demonstrated the enhancement of signal to noise ratio (SNR) by using of the polarization squeezed state (PSS) of 795 nm light field with Stokes operator S2 squeezed. PSS is prepared by locking the relative phase between the squeezed vacuum state of light obtained by a sub-threshold optical parametric oscillator and the orthogonal polarized local oscillator beam by means of the quantum noise lock. Under the same conditions, PSS can be employed not only to improve SNR, but also to keep the full width at half maximum (FWHM) of SNS unchanged, compared with the case of using polarization coherent state (PCS), and the enhancement of SNR is positively correlated with the squeezing level of PSS. With the increase of probe laser power and atomic number density, the SNR and FWHM of SNS will increase correspondingly. With the help of PSS of Stokes operator S2, quantum enhancement of both SNR and FWHM of SNS signal has been demonstrated by controlling optical power of the S2 polarization squeezed light beam or atomic number density in our experiments. △ Less

Submitted 18 November, 2021; originally announced November 2021.

Collision-induced spin noise

Authors: Shiming Song, Min Jiang, Yushu Qin, Yu Tong, Wenzhe Zhang, Xi Qin, Ren-Bao Liu, Xinhua Peng

Abstract: Collision phenomena are ubiquitous and of importance in determining the microscopic structures and intermolecular interactions of atoms and molecules. The existing approaches are mostly based on atomic or molecular scatterings, which are hindered by the inconvenience of using ultra-high vacuum and low temperature systems. Here we demonstrate a new spin-noise spectroscopic approach by measuring opt… ▽ More Collision phenomena are ubiquitous and of importance in determining the microscopic structures and intermolecular interactions of atoms and molecules. The existing approaches are mostly based on atomic or molecular scatterings, which are hindered by the inconvenience of using ultra-high vacuum and low temperature systems. Here we demonstrate a new spin-noise spectroscopic approach by measuring optical polarization rotation noise of the probe light, which operates with simple apparatus and ambient conditions. Our approach features tens of gigahertz bandwidth and one part-per-million resolution, outperforming existing spin-noise techniques. Enabled by the new technique, we observe the collision-induced spin noise of alkali atoms, and precisely determine key collision parameters, such as collision diameter, well depth, and dominant interaction type. Our work provides a new tool to study a broad range of collision phenomena under ambient conditions. △ Less

Submitted 10 July, 2021; originally announced July 2021.

Comments: 6 pages, 4 figures

Journal ref: Physical Review Applied. 2022 Jan 4;17(1):L011001

Confinement of long-lived interlayer excitons in WS$_2$/WSe$_2$ heterostructures

Authors: Alejandro R. -P. Montblanch, Dhiren M. Kara, Ioannis Paradisanos, Carola M. Purser, Matthew S. G. Feuer, Evgeny M. Alexeev, Lucio Stefan, Ying Qin, Mark Blei, Gang Wang, Alisson R. Cadore, Pawel Latawiec, Marko Lončar, Sefaattin Tongay, Andrea C. Ferrari, Mete Atatüre

Abstract: Interlayer excitons in layered materials constitute a novel platform to study many-body phenomena arising from long-range interactions between quantum particles. The ability to localise individual interlayer excitons in potential energy traps is a key step towards simulating Hubbard physics in artificial lattices. Here, we demonstrate spatial localisation of long-lived interlayer excitons in a str… ▽ More Interlayer excitons in layered materials constitute a novel platform to study many-body phenomena arising from long-range interactions between quantum particles. The ability to localise individual interlayer excitons in potential energy traps is a key step towards simulating Hubbard physics in artificial lattices. Here, we demonstrate spatial localisation of long-lived interlayer excitons in a strongly confining trap array using a WS$_{2}$/WSe$_{2}$ heterostructure on a nanopatterned substrate. We detect long-lived interlayer excitons with lifetime approaching 0.2 ms and show that their confinement results in a reduced lifetime in the microsecond range and stronger emission rate with sustained optical selection rules. The combination of a permanent dipole moment, spatial confinement and long lifetime places interlayer excitons in a regime that satisfies one of the requirements for observing long-range dynamics in an optically resolvable trap lattice. △ Less

Submitted 5 May, 2020; originally announced May 2020.

Quantum enhanced optical phase estimation with a squeezed thermal state

Authors: Juan Yu, Yue Qin, Jinliang Qin, Hong Wang, Zhihui Yan, Xiaojun Jia, Kunchi Peng

Abstract: Quantum phase estimation protocols can provide a measuring method of phase shift with precision superior to standard quantum limit (SQL) due to the application of a nonclassical state of light. A squeezed vacuum state, whose variance in one quadrature is lower than the corresponding SQL, has been pointed out a sensitive resource for quantum phase estimation and the estimation accuracy is directly… ▽ More Quantum phase estimation protocols can provide a measuring method of phase shift with precision superior to standard quantum limit (SQL) due to the application of a nonclassical state of light. A squeezed vacuum state, whose variance in one quadrature is lower than the corresponding SQL, has been pointed out a sensitive resource for quantum phase estimation and the estimation accuracy is directly influenced by the properties of the squeezed state. Here we detailedly analyze the influence of the purity and squeezing level of the squeezed state on the accuracy of quantum phase estimation. The maximum precision that can be achieved for a squeezed thermal state is evaluated, and the experimental results are in agreement with the theoretical analyses. It is also found that the width of the phase estimation interval $Δθ$ beyond SQL is correlated with the purity of the squeezed state. △ Less

Submitted 13 April, 2020; originally announced April 2020.

Comments: 7 pages, 5 figures

Journal ref: Phys. Rev. Applied 13, 024037 (2020)

Quantum-Secure Microgrid

Authors: Zefan Tang, Yanyuan Qin, Zimin Jiang, Walter O. Krawec, Peng Zhang

Abstract: Existing microgrid communication relies on classical public key systems, which are vulnerable to attacks from quantum computers. This paper uses quantum key distribution (QKD) to solve these quantum-era microgrid challenges. Specifically, this paper makes the following novel contributions: 1) it offers a QKD-based microgrid communication architecture for microgrids; 2) it shows how to build a quan… ▽ More Existing microgrid communication relies on classical public key systems, which are vulnerable to attacks from quantum computers. This paper uses quantum key distribution (QKD) to solve these quantum-era microgrid challenges. Specifically, this paper makes the following novel contributions: 1) it offers a QKD-based microgrid communication architecture for microgrids; 2) it shows how to build a quantum-secure microgrid testbed in an RTDS environment; 3) it develops a key pool sharing (KPS) strategy to improve the cyberattack resilience of the QKD-based microgrid; and 4) it analyzes the impacts of critical QKD parameters with the testbed. Test results provide insightful resources for building a quantum-secure microgrid. △ Less

Submitted 7 January, 2020; originally announced January 2020.

Several Localized Waves Induced by Linear Interference between a Nonlinear Plane Wave and Bright Solitons

Authors: Y. H. Qin, L. C. Zhao, Z. Y. Yang, W. L. Yang

Abstract: We investigate linear interference effects between a nonlinear plane wave and bright solitons, which are admitted by pair-transition coupled two-component Bose-Einstein condensate. We demonstrate the interference effects can induce several localized waves possessing distinctive wave structures, mainly including anti-dark soliton, W-shaped soliton, multi-peak soliton, Kuznetsov-Ma like breather, an… ▽ More We investigate linear interference effects between a nonlinear plane wave and bright solitons, which are admitted by pair-transition coupled two-component Bose-Einstein condensate. We demonstrate the interference effects can induce several localized waves possessing distinctive wave structures, mainly including anti-dark soliton, W-shaped soliton, multi-peak soliton, Kuznetsov-Ma like breather, and multi-peak breather. Especially, the explicit conditions for them are clarified by a phase diagram based on the linear interference properties. Furthermore, the interactions between these localized waves are discussed. The detailed analysis indicate that soliton-soliton interaction induced phase shift brings the collision between these localized waves be inelastic for soliton involving collision, and be elastic for breathers. These characters come from that the profile of solitons depend on relative phase between bright soliton and plane wave, and the profile of breathers do not depend on the relative phase. These results would motivate more discussions on linear interference between other nonlinear waves. Especially, the solitons or breathers obtained here are not related with modulational instability. The underlying reasons are discussed in detail. △ Less

Submitted 31 August, 2017; originally announced September 2017.

Comments: 8 pages, 7 figures

Journal ref: Chaos 28, 013111 (2018)

Enhanced quantum coherence in graphene caused by Pd cluster deposition

Authors: Yuyuan Qin, Junhao Han, Guoping Guo, Yongping Du, Zhaoguo Li, You Song, Li Pi, Xuefeng Wang, Xiangang Wan, Min Han, Fengqi Song

Abstract: We report on the unexpected increase in the dephasing lengths of a graphene sheet caused by the deposition of Pd nanoclusters, as demonstrated by weak localization measurements. The dephasing lengths reached saturated values at low temperatures. Theoretical calculations indicate the p-type charge transfer from the Pd clusters, which contributes more carriers. The saturated values of dephasing leng… ▽ More We report on the unexpected increase in the dephasing lengths of a graphene sheet caused by the deposition of Pd nanoclusters, as demonstrated by weak localization measurements. The dephasing lengths reached saturated values at low temperatures. Theoretical calculations indicate the p-type charge transfer from the Pd clusters, which contributes more carriers. The saturated values of dephasing lengths often depend on both the carrier concentration and mean free path. Although some impurities are increased as revealed by decreased mobilities, the intense charge transfer leads to the improved saturated values and subsequent improved dephasing lengths. △ Less

Submitted 5 January, 2015; v1 submitted 14 February, 2014; originally announced February 2014.

Comments: in press (APL)

Two-dimensional universal conductance fluctuations and the electron-phonon interaction of topological surface states in Bi2Te2Se nanoribbons

Authors: Zhaoguo Li, Taishi Chen, Haiyang Pan, Fengqi Song, Baigeng Wang, Junhao Han, Yuyuan Qin, Xuefeng Wang, Rong Zhang, Jianguo Wan, Dingyu Xing, Guanghou Wang

Abstract: The universal conductance fluctuations (UCFs), one of the most important manifestations of mesoscopic electronic interference, have not yet been demonstrated for the two-dimensional surface state of topological insulators (TIs). Even if one delicately suppresses the bulk conductance by improving the quality of TI crystals, the fluctuation of the bulk conductance still keeps competitive and difficu… ▽ More The universal conductance fluctuations (UCFs), one of the most important manifestations of mesoscopic electronic interference, have not yet been demonstrated for the two-dimensional surface state of topological insulators (TIs). Even if one delicately suppresses the bulk conductance by improving the quality of TI crystals, the fluctuation of the bulk conductance still keeps competitive and difficult to be separated from the desired UCFs of surface carriers. Here we report on the experimental evidence of the UCFs of the two-dimensional surface state in the bulk insulating Bi2Te2Se nanoribbons. The solely-B\perp-dependent UCF is achieved and its temperature dependence is investigated. The surface transport is further revealed by weak antilocalizations. Such survived UCFs of the topological surface states result from the limited dephasing length of the bulk carriers in ternary crystals. The electron-phonon interaction is addressed as a secondary source of the surface state dephasing based on the temperature-dependent scaling behavior. △ Less

Submitted 10 July, 2012; originally announced July 2012.

Journal ref: Scientific Report, 2, 595, 2012