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Measuring Reactive-Load Impedance with Transmission-Line Resonators Beyond the Perturbative Limit
Authors:
Xuanjing Chu,
Jinho Park,
Jesse Balgley,
Sean Clemons,
Ted S. Chung,
Kenji Watanabe,
Takashi Taniguchi,
Leonardo Ranzani,
Martin V. Gustafsson,
Kin Chung Fong,
James Hone
Abstract:
We develop an analytic framework to extract circuit parameters and loss tangent from superconducting transmission-line resonators terminated by reactive loads, extending analysis beyond the perturbative regime. The formulation yields closed-form relations between resonant frequency, participation ratio, and internal quality factor, removing the need for full-wave simulations. We validate the frame…
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We develop an analytic framework to extract circuit parameters and loss tangent from superconducting transmission-line resonators terminated by reactive loads, extending analysis beyond the perturbative regime. The formulation yields closed-form relations between resonant frequency, participation ratio, and internal quality factor, removing the need for full-wave simulations. We validate the framework through circuit simulations, finite-element modeling, and experimental measurements of van der Waals parallel-plate capacitors, using it to extract the dielectric constant and loss tangent of hexagonal boron nitride. Statistical analysis across multiple reference resonators, together with multimode self-calibration, demonstrates consistent and reproducible extraction of both capacitance and loss tangent in close agreement with literature values. In addition to parameter extraction, the analytic relations provide practical design guidelines for maximizing energy participation ratio in the load and improving the precision of resonator-based material metrology.
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Submitted 30 March, 2026; v1 submitted 18 November, 2025;
originally announced November 2025.
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Spontaneously Broken Non-Invertible Symmetries in Transverse-Field Ising Qudit Chains
Authors:
Kristian Tyn Kai Chung,
Umberto Borla,
Andriy H. Nevidomskyy,
Sergej Moroz
Abstract:
Recent developments have revealed that symmetries need not form a group, but instead can be non-invertible. Here we use analytical arguments and numerical evidence to illuminate how spontaneous symmetry breaking of a non-invertible symmetry is similar yet distinct from ordinary, invertible, symmetry breaking. We consider one-dimensional chains of group-valued qudits, whose local Hilbert space is s…
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Recent developments have revealed that symmetries need not form a group, but instead can be non-invertible. Here we use analytical arguments and numerical evidence to illuminate how spontaneous symmetry breaking of a non-invertible symmetry is similar yet distinct from ordinary, invertible, symmetry breaking. We consider one-dimensional chains of group-valued qudits, whose local Hilbert space is spanned by elements of a finite group $G$ (reducing to ordinary qubits when $G=\mathbb{Z}_2$). We construct Ising-type transverse-field Hamiltonians with Rep($G$) symmetry whose generators multiply according to the tensor product of irreducible representations (irreps) of the group $G$. For non-Abelian $G$, the symmetry is non-invertible. In the symmetry broken phase there is one ground state per irrep on a closed chain. The symmetry breaking can be detected by local order parameters but, unlike the invertible case, different ground states have distinct entanglement patterns. We show that for each irrep of dimension greater than one the corresponding ground state exhibits string order, entanglement spectrum degeneracies, and has gapless edge modes on an open chain -- features usually associated with symmetry-protected topological order. Consequently, domain wall excitations behave as one-dimensional non-Abelian anyons with non-trivial internal Hilbert spaces and fusion rules. Our work identifies properties of non-invertible symmetry breaking that existing quantum hardware can probe.
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Submitted 27 May, 2026; v1 submitted 14 August, 2025;
originally announced August 2025.
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Polarized and bright telecom C-band single-photon source from InP-based quantum dots coupled to elliptical Bragg gratings
Authors:
Zhenxuan Ge,
Tunghsun Chung,
Yu-Ming He,
Mohamed Benyoucef,
Yongheng Huo
Abstract:
Bright, polarized, and high-purity single-photon sources in telecom wavelengths are crucial components in long-distance quantum communication, optical quantum computation and quantum networks. Semiconductor InAs/InP quantum dots (QDs) combined with photonic cavities provide a competitive path leading to optimal single-photon sources in this range. Here, we demonstrate a bright and polarized single…
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Bright, polarized, and high-purity single-photon sources in telecom wavelengths are crucial components in long-distance quantum communication, optical quantum computation and quantum networks. Semiconductor InAs/InP quantum dots (QDs) combined with photonic cavities provide a competitive path leading to optimal single-photon sources in this range. Here, we demonstrate a bright and polarized single-photon source operating in the telecom C-band based on an elliptical Bragg grating (EBG) cavity. With a significant Purcell enhancement of 5.25$\pm$0.05, the device achieves a polarization ratio of 0.986, single-photon purity of g^2 (0)=0.078$\pm$0.016 and single-polarized photon collection efficiency of ~ 24% at the first lens (NA=0.65) without blinking. These findings suggest that C-band QD-based single-photon sources are potential candidates for advancing quantum communication.
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Submitted 25 January, 2024;
originally announced January 2024.
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Experimental quantum non-Gaussian coincidences of entangled photons
Authors:
Run-Ze Liu,
Yu-Kun Qiao,
Lukáš Lachman,
Zhen-Xuan Ge,
Tung-Hsun Chung,
Jun-Yi Zhao,
Hao Li,
Lixing You,
Radim Filip,
Yong-Heng Huo
Abstract:
Quantum non-Gaussianity, a more potent and highly useful form of nonclassicality, excludes all convex mixtures of Gaussian states and Gaussian parametric processes generating them. Here, for the first time, we conclusively test quantum non-Gaussian coincidences of entangled photon pairs with the CHSH-Bell factor $S=2.328\pm0.004$ from a single quantum dot with a depth up to $0.94\pm 0.02$ dB. Such…
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Quantum non-Gaussianity, a more potent and highly useful form of nonclassicality, excludes all convex mixtures of Gaussian states and Gaussian parametric processes generating them. Here, for the first time, we conclusively test quantum non-Gaussian coincidences of entangled photon pairs with the CHSH-Bell factor $S=2.328\pm0.004$ from a single quantum dot with a depth up to $0.94\pm 0.02$ dB. Such deterministically generated photon pairs fundamentally overcome parametric processes by reducing crucial multiphoton errors. For the quantum non-Gaussian depth of the unheralded (heralded) single-photon state, we achieve the value of $8.08\pm0.05$ dB ($19.06\pm0.29$ dB). Our work experimentally certifies the exclusive quantum non-Gaussianity properties highly relevant for optical sensing, communication and computation.
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Submitted 25 January, 2024; v1 submitted 10 July, 2023;
originally announced July 2023.
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Logical Magic State Preparation with Fidelity Beyond the Distillation Threshold on a Superconducting Quantum Processor
Authors:
Yangsen Ye,
Tan He,
He-Liang Huang,
Zuolin Wei,
Yiming Zhang,
Youwei Zhao,
Dachao Wu,
Qingling Zhu,
Huijie Guan,
Sirui Cao,
Fusheng Chen,
Tung-Hsun Chung,
Hui Deng,
Daojin Fan,
Ming Gong,
Cheng Guo,
Shaojun Guo,
Lianchen Han,
Na Li,
Shaowei Li,
Yuan Li,
Futian Liang,
Jin Lin,
Haoran Qian,
Hao Rong
, et al. (13 additional authors not shown)
Abstract:
Fault-tolerant quantum computing based on surface code has emerged as an attractive candidate for practical large-scale quantum computers to achieve robust noise resistance. To achieve universality, magic states preparation is a commonly approach for introducing non-Clifford gates. Here, we present a hardware-efficient and scalable protocol for arbitrary logical state preparation for the rotated s…
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Fault-tolerant quantum computing based on surface code has emerged as an attractive candidate for practical large-scale quantum computers to achieve robust noise resistance. To achieve universality, magic states preparation is a commonly approach for introducing non-Clifford gates. Here, we present a hardware-efficient and scalable protocol for arbitrary logical state preparation for the rotated surface code, and further experimentally implement it on the \textit{Zuchongzhi} 2.1 superconducting quantum processor. An average of \hhl{$0.8983 \pm 0.0002$} logical fidelity at different logical states with distance-three is achieved, \hhl{taking into account both state preparation and measurement errors.} In particular, \hhl{the magic states $|A^{π/4}\rangle_L$, $|H\rangle_L$, and $|T\rangle_L$ are prepared non-destructively with logical fidelities of $0.8771 \pm 0.0009 $, $0.9090 \pm 0.0009 $, and $0.8890 \pm 0.0010$, respectively, which are higher than the state distillation protocol threshold, 0.859 (for H-type magic state) and 0.827 (for T -type magic state).} Our work provides a viable and efficient avenue for generating high-fidelity raw logical magic states, which is essential for realizing non-Clifford logical gates in the surface code.
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Submitted 30 May, 2023; v1 submitted 25 May, 2023;
originally announced May 2023.
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Eliminating temporal correlation in quantum-dot entangled photon source by quantum interference
Authors:
Run-Ze Liu,
Yu-Kun Qiao,
Han-Sen Zhong,
Zhen-Xuan Ge,
Hui Wang,
Tung-Hsun Chung,
Chao-Yang Lu,
Yong-Heng Huo,
Jian-Wei Pan
Abstract:
Semiconductor quantum dots, as promising solid-state platform, have exhibited deterministic photon pair generation with high polarization entanglement f\textcompwordmark idelity for quantum information applications. However, due to temporal correlation from inherently cascaded emission, photon indistinguishability is limited, which restricts their potential scalability to multi-photon experiments.…
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Semiconductor quantum dots, as promising solid-state platform, have exhibited deterministic photon pair generation with high polarization entanglement f\textcompwordmark idelity for quantum information applications. However, due to temporal correlation from inherently cascaded emission, photon indistinguishability is limited, which restricts their potential scalability to multi-photon experiments. Here, by utilizing quantum interferences to decouple polarization entanglement from temporal correlation, we improve multi-photon entanglement f\textcompwordmark idelity from $(58.7\pm 2.2)\%$ to $(75.5\pm 2.0)\%$. Our work paves the way to realize scalable and high-quality multi-photon states from quantum dots.
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Submitted 26 December, 2022;
originally announced December 2022.
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Experimental quantum computational chemistry with optimised unitary coupled cluster ansatz
Authors:
Shaojun Guo,
Jinzhao Sun,
Haoran Qian,
Ming Gong,
Yukun Zhang,
Fusheng Chen,
Yangsen Ye,
Yulin Wu,
Sirui Cao,
Kun Liu,
Chen Zha,
Chong Ying,
Qingling Zhu,
He-Liang Huang,
Youwei Zhao,
Shaowei Li,
Shiyu Wang,
Jiale Yu,
Daojin Fan,
Dachao Wu,
Hong Su,
Hui Deng,
Hao Rong,
Yuan Li,
Kaili Zhang
, et al. (13 additional authors not shown)
Abstract:
Quantum computational chemistry has emerged as an important application of quantum computing. Hybrid quantum-classical computing methods, such as variational quantum eigensolvers (VQE), have been designed as promising solutions to quantum chemistry problems, yet challenges due to theoretical complexity and experimental imperfections hinder progress in achieving reliable and accurate results. Exper…
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Quantum computational chemistry has emerged as an important application of quantum computing. Hybrid quantum-classical computing methods, such as variational quantum eigensolvers (VQE), have been designed as promising solutions to quantum chemistry problems, yet challenges due to theoretical complexity and experimental imperfections hinder progress in achieving reliable and accurate results. Experimental works for solving electronic structures are consequently still restricted to nonscalable (hardware efficient) or classically simulable (Hartree-Fock) ansatz, or limited to a few qubits with large errors. The experimental realisation of scalable and high-precision quantum chemistry simulation remains elusive. Here, we address the critical challenges {associated with} solving molecular electronic structures using noisy quantum processors. Our protocol presents significant improvements in the circuit depth and running time, key metrics for chemistry simulation. Through systematic hardware enhancements and the integration of error mitigation techniques, we push forward the limit of experimental quantum computational chemistry and successfully scale up the implementation of VQE with an optimised unitary coupled-cluster ansatz to 12 qubits. We produce high-precision results of the ground-state energy for molecules with error suppression by around two orders of magnitude. We achieve chemical accuracy for H$_2$ at all bond distances and LiH at small bond distances in the experiment, even beyond the two recent concurrent works. Our work demonstrates a feasible path towards a scalable solution to electronic structure calculation, validating the key technological features and identifying future challenges for this goal.
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Submitted 17 June, 2024; v1 submitted 15 December, 2022;
originally announced December 2022.
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Realization of an Error-Correcting Surface Code with Superconducting Qubits
Authors:
Youwei Zhao,
Yangsen Ye,
He-Liang Huang,
Yiming Zhang,
Dachao Wu,
Huijie Guan,
Qingling Zhu,
Zuolin Wei,
Tan He,
Sirui Cao,
Fusheng Chen,
Tung-Hsun Chung,
Hui Deng,
Daojin Fan,
Ming Gong,
Cheng Guo,
Shaojun Guo,
Lianchen Han,
Na Li,
Shaowei Li,
Yuan Li,
Futian Liang,
Jin Lin,
Haoran Qian,
Hao Rong
, et al. (14 additional authors not shown)
Abstract:
Quantum error correction is a critical technique for transitioning from noisy intermediate-scale quantum (NISQ) devices to fully fledged quantum computers. The surface code, which has a high threshold error rate, is the leading quantum error correction code for two-dimensional grid architecture. So far, the repeated error correction capability of the surface code has not been realized experimental…
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Quantum error correction is a critical technique for transitioning from noisy intermediate-scale quantum (NISQ) devices to fully fledged quantum computers. The surface code, which has a high threshold error rate, is the leading quantum error correction code for two-dimensional grid architecture. So far, the repeated error correction capability of the surface code has not been realized experimentally. Here, we experimentally implement an error-correcting surface code, the distance-3 surface code which consists of 17 qubits, on the \textit{Zuchongzhi} 2.1 superconducting quantum processor. By executing several consecutive error correction cycles, the logical error can be significantly reduced after applying corrections, achieving the repeated error correction of surface code for the first time. This experiment represents a fully functional instance of an error-correcting surface code, providing a key step on the path towards scalable fault-tolerant quantum computing.
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Submitted 29 January, 2022; v1 submitted 26 December, 2021;
originally announced December 2021.
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Quantum Computational Advantage via 60-Qubit 24-Cycle Random Circuit Sampling
Authors:
Qingling Zhu,
Sirui Cao,
Fusheng Chen,
Ming-Cheng Chen,
Xiawei Chen,
Tung-Hsun Chung,
Hui Deng,
Yajie Du,
Daojin Fan,
Ming Gong,
Cheng Guo,
Chu Guo,
Shaojun Guo,
Lianchen Han,
Linyin Hong,
He-Liang Huang,
Yong-Heng Huo,
Liping Li,
Na Li,
Shaowei Li,
Yuan Li,
Futian Liang,
Chun Lin,
Jin Lin,
Haoran Qian
, et al. (28 additional authors not shown)
Abstract:
To ensure a long-term quantum computational advantage, the quantum hardware should be upgraded to withstand the competition of continuously improved classical algorithms and hardwares. Here, we demonstrate a superconducting quantum computing systems \textit{Zuchongzhi} 2.1, which has 66 qubits in a two-dimensional array in a tunable coupler architecture. The readout fidelity of \textit{Zuchongzhi}…
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To ensure a long-term quantum computational advantage, the quantum hardware should be upgraded to withstand the competition of continuously improved classical algorithms and hardwares. Here, we demonstrate a superconducting quantum computing systems \textit{Zuchongzhi} 2.1, which has 66 qubits in a two-dimensional array in a tunable coupler architecture. The readout fidelity of \textit{Zuchongzhi} 2.1 is considerably improved to an average of 97.74\%. The more powerful quantum processor enables us to achieve larger-scale random quantum circuit sampling, with a system scale of up to 60 qubits and 24 cycles. The achieved sampling task is about 6 orders of magnitude more difficult than that of Sycamore [Nature \textbf{574}, 505 (2019)] in the classic simulation, and 3 orders of magnitude more difficult than the sampling task on \textit{Zuchongzhi} 2.0 [arXiv:2106.14734 (2021)]. The time consumption of classically simulating random circuit sampling experiment using state-of-the-art classical algorithm and supercomputer is extended to tens of thousands of years (about $4.8\times 10^4$ years), while \textit{Zuchongzhi} 2.1 only takes about 4.2 hours, thereby significantly enhancing the quantum computational advantage.
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Submitted 9 September, 2021; v1 submitted 8 September, 2021;
originally announced September 2021.
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Quantum interference between independent solid-state single-photon sources separated by 300 km fiber
Authors:
Xiang You,
Ming-Yang Zheng,
Si Chen,
Run-Ze Liu,
Jian Qin,
M. -C. Xu,
Z. -X. Ge,
T. -H. Chung,
Y. -K. Qiao,
Y. -F. Jiang,
H. -S. Zhong,
M. -C. Chen,
H. Wang,
Y. -M. He,
X. -P. Xie,
H. Li,
L. -X. You,
C. Schneider,
J. Yin,
T. -Y. Chen,
M. Benyoucef,
Yong-Heng Huo,
S. Hoefling,
Qiang Zhang,
Chao-Yang Lu
, et al. (1 additional authors not shown)
Abstract:
In the quest to realize a scalable quantum network, semiconductor quantum dots (QDs) offer distinct advantages including high single-photon efficiency and indistinguishability, high repetition rate (tens of GHz with Purcell enhancement), interconnectivity with spin qubits, and a scalable on-chip platform. However, in the past two decades, the visibility of quantum interference between independent…
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In the quest to realize a scalable quantum network, semiconductor quantum dots (QDs) offer distinct advantages including high single-photon efficiency and indistinguishability, high repetition rate (tens of GHz with Purcell enhancement), interconnectivity with spin qubits, and a scalable on-chip platform. However, in the past two decades, the visibility of quantum interference between independent QDs rarely went beyond the classical limit of 50$\%$ and the distances were limited from a few meters to kilometers. Here, we report quantum interference between two single photons from independent QDs separated by 302 km optical fiber. The single photons are generated from resonantly driven single QDs deterministically coupled to microcavities. Quantum frequency conversions are used to eliminate the QD inhomogeneity and shift the emission wavelength to the telecommunication band. The observed interference visibility is 0.67$\pm$0.02 (0.93$\pm$0.04) without (with) temporal filtering. Feasible improvements can further extend the distance to 600 km. Our work represents a key step to long-distance solid-state quantum networks.
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Submitted 29 June, 2021;
originally announced June 2021.
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Strong quantum computational advantage using a superconducting quantum processor
Authors:
Yulin Wu,
Wan-Su Bao,
Sirui Cao,
Fusheng Chen,
Ming-Cheng Chen,
Xiawei Chen,
Tung-Hsun Chung,
Hui Deng,
Yajie Du,
Daojin Fan,
Ming Gong,
Cheng Guo,
Chu Guo,
Shaojun Guo,
Lianchen Han,
Linyin Hong,
He-Liang Huang,
Yong-Heng Huo,
Liping Li,
Na Li,
Shaowei Li,
Yuan Li,
Futian Liang,
Chun Lin,
Jin Lin
, et al. (29 additional authors not shown)
Abstract:
Scaling up to a large number of qubits with high-precision control is essential in the demonstrations of quantum computational advantage to exponentially outpace the classical hardware and algorithmic improvements. Here, we develop a two-dimensional programmable superconducting quantum processor, \textit{Zuchongzhi}, which is composed of 66 functional qubits in a tunable coupling architecture. To…
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Scaling up to a large number of qubits with high-precision control is essential in the demonstrations of quantum computational advantage to exponentially outpace the classical hardware and algorithmic improvements. Here, we develop a two-dimensional programmable superconducting quantum processor, \textit{Zuchongzhi}, which is composed of 66 functional qubits in a tunable coupling architecture. To characterize the performance of the whole system, we perform random quantum circuits sampling for benchmarking, up to a system size of 56 qubits and 20 cycles. The computational cost of the classical simulation of this task is estimated to be 2-3 orders of magnitude higher than the previous work on 53-qubit Sycamore processor [Nature \textbf{574}, 505 (2019)]. We estimate that the sampling task finished by \textit{Zuchongzhi} in about 1.2 hours will take the most powerful supercomputer at least 8 years. Our work establishes an unambiguous quantum computational advantage that is infeasible for classical computation in a reasonable amount of time. The high-precision and programmable quantum computing platform opens a new door to explore novel many-body phenomena and implement complex quantum algorithms.
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Submitted 28 June, 2021;
originally announced June 2021.
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Towards optimal single-photon sources from polarized microcavities
Authors:
Hui Wang,
Yu-Ming He,
Tung Hsun Chung,
Hai Hu,
Ying Yu,
Si Chen,
Xing Ding,
Ming-Cheng Chen,
Jian Qin,
Xiaoxia Yang,
Run-Ze Liu,
Zhao-Chen Duan,
Jin-Peng Li,
Stefan Gerhardt,
Karol Winkler,
Jonathan Jurkat,
Lin-Jun Wang,
Niels Gregersen,
Yong-Heng Huo,
Qing Dai,
Siyuan Yu,
Sven Hoefling,
Chao-Yang Lu,
Jian-Wei Pan
Abstract:
An optimal single-photon source should deterministically deliver one and only one photon at a time, with no trade-off between the source's efficiency and the photon indistinguishability. However, all reported solid-state sources of indistinguishable single photons had to rely on polarization filtering which reduced the efficiency by 50%, which fundamentally limited the scaling of photonic quantum…
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An optimal single-photon source should deterministically deliver one and only one photon at a time, with no trade-off between the source's efficiency and the photon indistinguishability. However, all reported solid-state sources of indistinguishable single photons had to rely on polarization filtering which reduced the efficiency by 50%, which fundamentally limited the scaling of photonic quantum technologies. Here, we overcome this final long-standing challenge by coherently driving quantum dots deterministically coupled to polarization-selective Purcell microcavities--two examples are narrowband, elliptical micropillars and broadband, elliptical Bragg gratings. A polarization-orthogonal excitation-collection scheme is designed to minimize the polarization-filtering loss under resonant excitation. We demonstrate a polarized single-photon efficiency of 0.60+/-0.02 (0.56+/-0.02), a single-photon purity of 0.975+/-0.005 (0.991+/-0.003), and an indistinguishability of 0.975+/-0.006 (0.951+/-0.005) for the micropillar (Bragg grating) device. Our work provides promising solutions for truly optimal single-photon sources combining near-unity indistinguishability and near-unity system efficiency simultaneously.
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Submitted 15 July, 2019;
originally announced July 2019.
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On-demand semiconductor source of entangled photons which simultaneously has high fidelity, efficiency, and indistinguishability
Authors:
Hui Wang,
Hai Hu,
T. -H. Chung,
Jian Qin,
Xiaoxia Yang,
J. -P. Li,
R. -Z. Liu,
H. -S. Zhong,
Y. -M. He,
Xing Ding,
Y. -H. Deng,
C. Schneider,
Qing Dai,
Y. -H. Huo,
Sven Höfling,
Chao-Yang Lu,
Jian-Wei Pan
Abstract:
An outstanding goal in quantum optics and scalable photonic quantum technology is to develop a source that each time emits one and only one entangled photon pair with simultaneously high entanglement fidelity, extraction efficiency, and photon indistinguishability. By coherent two-photon excitation of a single InGaAs quantum dot coupled to a circular Bragg grating bullseye cavity with broadband hi…
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An outstanding goal in quantum optics and scalable photonic quantum technology is to develop a source that each time emits one and only one entangled photon pair with simultaneously high entanglement fidelity, extraction efficiency, and photon indistinguishability. By coherent two-photon excitation of a single InGaAs quantum dot coupled to a circular Bragg grating bullseye cavity with broadband high Purcell factor up to 11.3, we generate entangled photon pairs with a state fidelity of 0.90(1), pair generation rate of 0.59(1), pair extraction efficiency of 0.62(6), and photon indistinguishability of 0.90(1) simultaneously. Our work will open up many applications in high-efficiency multi-photon experiments and solid-state quantum repeaters.
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Submitted 14 March, 2019;
originally announced March 2019.
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Statistical study of stacked/coupled site-controlled pyramidal quantum dots and their excitonic properties
Authors:
S. T. Moroni,
T. H. Chung,
G. Juska,
A. Gocalinska,
E. Pelucchi
Abstract:
We report on stacked multiple quantum dots (QDs) formed inside inverted pyramidal recesses, which allow for the precise positioning of the QDs themselves. Specifically we fabricated double QDs with varying inter-dot distance and ensembles with more than two nominally highly symmetric QDs. For each, the effect of the interaction between QDs is studied by characterizing a large number of QDs through…
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We report on stacked multiple quantum dots (QDs) formed inside inverted pyramidal recesses, which allow for the precise positioning of the QDs themselves. Specifically we fabricated double QDs with varying inter-dot distance and ensembles with more than two nominally highly symmetric QDs. For each, the effect of the interaction between QDs is studied by characterizing a large number of QDs through photoluminescence spectroscopy. A clear red-shift of the emission energy is observed together with a change in the orientation of its polarization, suggesting an increasing interaction between the QDs. Finally we show how stacked QDs can help influencing the charging of the excitonic complexes.
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Submitted 31 August, 2017;
originally announced August 2017.
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Engineering of selective carrier injection in patterned arrays of single-quantum-dot entangled photon light-emitting diodes
Authors:
T-H. Chung,
G. Juska,
S. T. Moroni,
A. Pescaglini,
A. Gocalinska,
E. Pelucchi
Abstract:
Scalability and foundry compatibility (as for example in conventional silicon based integrated computer processors) in developing quantum technologies are exceptional challenges facing current research. Here we introduce a quantum photonic technology potentially enabling large scale fabrication of semiconductor-based, site-controlled, scalable arrays of electrically driven sources of polarization-…
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Scalability and foundry compatibility (as for example in conventional silicon based integrated computer processors) in developing quantum technologies are exceptional challenges facing current research. Here we introduce a quantum photonic technology potentially enabling large scale fabrication of semiconductor-based, site-controlled, scalable arrays of electrically driven sources of polarization-entangled photons, with the potential to encode quantum information. The design of the sources is based on quantum dots grown in micron-sized pyramidal recesses along the crystallographic direction (111)B theoretically ensuring high symmetry of the quantum dots - the condition for actual bright entangled photon emission. A selective electric injection scheme in these non-planar structures allows obtaining a high density of light-emitting diodes, with some producing entangled photon pairs also violating Bell's inequality. Compatibility with semiconductor fabrication technology, good reproducibility and control of the position make these devices attractive candidates for integrated photonic circuits for quantum information processing.
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Submitted 19 July, 2017;
originally announced July 2017.
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Conditions for entangled photon emission from (111)B site-controlled Pyramidal quantum dots
Authors:
G. Juska,
E. Murray,
V. Dimastrodonato,
T. H. Chung,
S. Moroni,
A. Gocalinska,
E. Pelucchi
Abstract:
A study of highly symmetric site-controlled Pyramidal In0.25Ga0.75As quantum dots (QDs) is presented. It is discussed that polarization-entangled photons can be also obtained from Pyramidal QDs of different designs from the one already reported in Juska et al. (Nat. Phot. 7, 527, 2013). Moreover, some of the limitations for a higher density of entangled photon emitters are addressed. Among these i…
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A study of highly symmetric site-controlled Pyramidal In0.25Ga0.75As quantum dots (QDs) is presented. It is discussed that polarization-entangled photons can be also obtained from Pyramidal QDs of different designs from the one already reported in Juska et al. (Nat. Phot. 7, 527, 2013). Moreover, some of the limitations for a higher density of entangled photon emitters are addressed. Among these issues are (1) a remaining small fine-structure splitting and (2) an effective QD charging under non-resonant excitation conditions, which strongly reduce the number of useful biexciton-exciton recombination events. A possible solution of the charging problem is investigated exploiting a dual-wavelength excitation technique, which allows a gradual QD charge tuning from strongly negative to positive and, eventually, efficient detection of entangled photons from QDs, which would be otherwise ineffective under a single-wavelength (non-resonant) excitation.
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Submitted 13 February, 2015;
originally announced February 2015.
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Characterizing measurement-based quantum gates in quantum many-body systems using correlation functions
Authors:
Thomas Chung,
Stephen D. Bartlett,
Andrew C. Doherty
Abstract:
In measurement-based quantum computation (MBQC), local adaptive measurements are performed on the quantum state of a lattice of qubits. Quantum gates are associated with a particular measurement sequence, and one way of viewing MBQC is that such a measurement sequence prepares a resource state suitable for `gate teleportation'. We demonstrate how to quantify the performance of quantum gates in M…
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In measurement-based quantum computation (MBQC), local adaptive measurements are performed on the quantum state of a lattice of qubits. Quantum gates are associated with a particular measurement sequence, and one way of viewing MBQC is that such a measurement sequence prepares a resource state suitable for `gate teleportation'. We demonstrate how to quantify the performance of quantum gates in MBQC by using correlation functions on the pre-measurement resource state.
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Submitted 16 April, 2009;
originally announced April 2009.