EPJ Quantum Technology最新文献

{"title":"Multiple electron pumping","authors":"Mark D. Blumenthal,&nbsp;Declan Mahony,&nbsp;Salahuddeen Ahmad,&nbsp;Dominique Gouveia,&nbsp;Hume Howe,&nbsp;Harvey E. Beere,&nbsp;Thomas Mitchel,&nbsp;Dave A. Ritchie,&nbsp;Michael Pepper","doi":"10.1140/epjqt/s40507-023-00203-z","DOIUrl":"10.1140/epjqt/s40507-023-00203-z","url":null,"abstract":"<div><p>The need to pump single electrons with a high degree of accuracy and fidelity has led to the development of a range of different pump and turnstile designs. Previous pumping mechanisms have all demonstrated that pumping more than one electron per cycle degrades the quantisation of the measured current. This unreliable delivery of multiple electrons per cycle has limited the use of on-demand single electron sources in electron quantum optic experiments. We present highly quantised current with multiple electrons pumped per cycle. We experimentally demonstrate that in our pumps an increase in electron throughput per cycle does not lead to an appreciable degradation in the accuracy of the produced current.</p><p>Our pump is realised in an aluminium gallium arsenide two-dimensional electron gas, where electrons are pumped through a one-dimensional split-gate confinement potential under the influence of an applied source-drain voltage <span>(V_{text{SD}})</span>, and where the pump is driven by a trapezoidal arbitrary waveform. This combination of a split-gate potential, <span>(V_{text{SD}})</span> bias and trapezoidal wave form has led to the observation of robust quantised plateaus where not just a single electron, but a multiple integer number of electrons are pumped per cycle with a high degree of robustness and without the need of a magnetic field. For seven electrons per cycle, we report an increase of over two orders of magnitude in pumping accuracy from <span>(2.72 times 10^{-2})</span> in devices operating in the conventional pumping regime, to <span>(1.64 times 10^{-4})</span> in pumps operating in what we call the long plateau regime, a regime accessed under a change in a split-gate pumps applied <span>(V_{text{SD}})</span> voltage. This pump will find direct use in quantum transport measurements where the metrological accuracy of single electrons pumped per cycle is not required and the low throughput per cycle of electrons is limiting.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":null,"pages":null},"PeriodicalIF":5.3,"publicationDate":"2023-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00203-z","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134797891","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Soft syndrome iterative decoding of quantum LDPC codes and hardware architectures","authors":"Nithin Raveendran,&nbsp;Javier Valls,&nbsp;Asit Kumar Pradhan,&nbsp;Narayanan Rengaswamy,&nbsp;Francisco Garcia-Herrero,&nbsp;Bane Vasić","doi":"10.1140/epjqt/s40507-023-00201-1","DOIUrl":"10.1140/epjqt/s40507-023-00201-1","url":null,"abstract":"<div><p>In practical quantum error correction implementations, the measurement of syndrome information is an unreliable step—typically modeled as a binary measurement outcome flipped with some probability. However, the measured syndrome is in fact a discretized value of the continuous voltage or current values obtained in the physical implementation of the syndrome extraction. In this paper, we use this “soft” or analog information to benefit iterative decoders for decoding quantum low-density parity-check (QLDPC) codes. Syndrome-based iterative belief propagation decoders are modified to utilize the soft syndrome to correct both data and syndrome errors simultaneously. We demonstrate the advantages of the proposed scheme not only in terms of comparison of thresholds and logical error rates for quasi-cyclic lifted-product QLDPC code families but also with faster convergence of iterative decoders. Additionally, we derive hardware (FPGA) architectures of these soft syndrome decoders and obtain similar performance in terms of error correction to the ideal models even with reduced precision in the soft information. The total latency of the hardware architectures is about 600 ns (for the QLDPC codes considered) in a 20 nm CMOS process FPGA device, and the area overhead is almost constant—less than 50% compared to min-sum decoders with noisy syndromes.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":null,"pages":null},"PeriodicalIF":5.3,"publicationDate":"2023-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00201-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134878380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Improving quantum annealing by engineering the coupling to the environment","authors":"Mojdeh S. Najafabadi,&nbsp;Daniel Schumayer,&nbsp;Chee-Kong Lee,&nbsp;Dieter Jaksch,&nbsp;David A. W. Hutchinson","doi":"10.1140/epjqt/s40507-023-00202-0","DOIUrl":"10.1140/epjqt/s40507-023-00202-0","url":null,"abstract":"<div><p>A large class of optimisation problems can be mapped to the Ising model where all details are encoded in the coupling of spins. The task of the original mathematical optimisation is then equivalent to finding the ground state of the corresponding spin system which can be achieved via quantum annealing relying on the adiabatic theorem. Some of the inherent disadvantages of this procedure can be alleviated or resolved using a stochastic approach, and by coupling to the external environment. We show that careful engineering of the system-bath coupling at an <i>individual</i> spin level can further improve annealing.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":null,"pages":null},"PeriodicalIF":5.3,"publicationDate":"2023-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00202-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134796863","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multi-bit quantum random number generator from path-entangled single photons","authors":"K. Muhammed Shafi,&nbsp;Prateek Chawla,&nbsp;Abhaya S. Hegde,&nbsp;R. S. Gayatri,&nbsp;A. Padhye,&nbsp;C. M. Chandrashekar","doi":"10.1140/epjqt/s40507-023-00200-2","DOIUrl":"10.1140/epjqt/s40507-023-00200-2","url":null,"abstract":"<div><p>Measurement outcomes on quantum systems exhibit inherent randomness and are fundamentally nondeterministic. This has enabled quantum physics to set new standards for the generation of true randomness with significant applications in the fields of cryptography, statistical simulations, and modeling of the nondeterministic behavior in various other fields. In this work, we present a scheme for the generation of multi-bit random numbers using path-entangled single photons. For the experimental demonstration, we generate a path-entangled state using single photons from spontaneous parametric down-conversion (SPDC) and assign a multi-qubit state for them in path basis. One-bit and two-bit random numbers are then generated by measuring entangled states in the path basis. In addition to passing the NIST tests for randomness, we also demonstrate the certification of quantumness and self-certification of quantum random number generator (QRNG) using Clauser, Horne, Shimony and Holt (CHSH) inequality violation. We also record the significantly low autocorrelation coefficient from the raw bits generated and this along with CHSH violation rules out multi-photon events and ensure the protection from photon splitting attack. Distribution of photons along multiple paths resulting in multiple bits from one photon extends the limit on bit generation rate imposed by the detection dead time of the individual detector. Thus, the path-entangled states can generate higher bitrates compared to scheme using entangled photon pair which are limited by the coincidence counts. We demonstrate this by generating a high rate of about 80 Mbps when the single photon detector saturates at around 28 Mcps and still show violation of CHSH inequality.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":null,"pages":null},"PeriodicalIF":5.3,"publicationDate":"2023-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00200-2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134796462","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Correction: Optimising the quantum/classical interface for efficiency and portability with a multi-level hardware abstraction layer for quantum computers","authors":"Kenton M. Barnes,&nbsp;Anton Buyskikh,&nbsp;Nicholas Y. Chen,&nbsp;Gabriel Gallardo,&nbsp;Marco Ghibaudi,&nbsp;Matthew J. A. Ruszala,&nbsp;Daniel S. Underwood,&nbsp;Abhishek Agarwal,&nbsp;Deep Lall,&nbsp;Ivan Rungger,&nbsp;Nikolaos Schoinas","doi":"10.1140/epjqt/s40507-023-00196-9","DOIUrl":"10.1140/epjqt/s40507-023-00196-9","url":null,"abstract":"","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":null,"pages":null},"PeriodicalIF":5.3,"publicationDate":"2023-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00196-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134795893","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Information reconciliation of continuous-variables quantum key distribution: principles, implementations and applications","authors":"Shenshen Yang,&nbsp;Zhilei Yan,&nbsp;Hongzhao Yang,&nbsp;Qing Lu,&nbsp;Zhenguo Lu,&nbsp;Liuyong Cheng,&nbsp;Xiangyang Miao,&nbsp;Yongmin Li","doi":"10.1140/epjqt/s40507-023-00197-8","DOIUrl":"10.1140/epjqt/s40507-023-00197-8","url":null,"abstract":"<div><p>Quantum key distribution (QKD) can provide information-theoretically secure keys for two parties of legitimate communication, and information reconciliation, as an indispensable component of QKD systems, can correct errors present in raw keys based on error-correcting codes. In this paper, we first describe the basic knowledge of information reconciliation and its impact on continuous variable QKD. Then we introduce the information schemes and the corresponding error correction codes employed. Next, we introduce the rate-compatible codes, the hardware acceleration of the reconciliation algorithm, the research progress of information reconciliation, and its application in continuous variable QKD. Finally, we discuss the future challenges and conclude.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":null,"pages":null},"PeriodicalIF":5.3,"publicationDate":"2023-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00197-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134795640","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Performance of high impedance resonators in dirty dielectric environments","authors":"J. H. Ungerer,&nbsp;D. Sarmah,&nbsp;A. Kononov,&nbsp;J. Ridderbos,&nbsp;R. Haller,&nbsp;L. Y. Cheung,&nbsp;C. Schönenberger","doi":"10.1140/epjqt/s40507-023-00199-6","DOIUrl":"10.1140/epjqt/s40507-023-00199-6","url":null,"abstract":"<div><p>High-impedance resonators are a promising contender for realizing long-distance entangling gates between spin qubits. Often, the fabrication of spin qubits relies on the use of gate dielectrics which are detrimental to the quality of the resonator. Here, we investigate loss mechanisms of high-impedance NbTiN resonators in the vicinity of thermally grown SiO₂ and Al₂O₃ fabricated by atomic layer deposition. We benchmark the resonator performance in elevated magnetic fields and at elevated temperatures and find that the internal quality factors are limited by the coupling between the resonator and two-level systems of the employed oxides. Nonetheless, the internal quality factors of high-impedance resonators exceed 10³ in all investigated oxide configurations which implies that the dielectric configuration would not limit the performance of resonators integrated in a spin-qubit device. Because these oxides are commonly used for spin qubit device fabrication, our results allow for straightforward integration of high-impedance resonators into spin-based quantum processors. Hence, these experiments pave the way for large-scale, spin-based quantum computers.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":null,"pages":null},"PeriodicalIF":5.3,"publicationDate":"2023-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10558395/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41104414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quantum scaling atomic superheterodyne receiver","authors":"Peng Zhang,&nbsp;Mingyong Jing,&nbsp;Zheng Wang,&nbsp;Yan Peng,&nbsp;Shaoxin Yuan,&nbsp;Hao Zhang,&nbsp;Liantuan Xiao,&nbsp;Suotang Jia,&nbsp;Linjie Zhang","doi":"10.1140/epjqt/s40507-023-00198-7","DOIUrl":"10.1140/epjqt/s40507-023-00198-7","url":null,"abstract":"<div><p>Measurement sensitivity is one of the critical indicators for Rydberg atomic radio receivers. This work quantitatively studies the relationship between the atomic superheterodyne receiver’s sensitivity and the number of atoms involved in the measurement. The atom number is changed by adjusting the length of the interaction area. The results show that for the ideal case where only interaction noise is present and the RF waves are uniformly distributed, the sensitivity of the atomic superheterodyne receiver exhibits a quantum scaling: the amplitude of its output signal is proportional to the atom number, and the amplitude of its read-out noise is proportional to the square root of the atom number. Hence, its sensitivity is inversely proportional to the square root of the atom number. This work also gives a detailed discussion of the properties of transit noise in atomic receivers and the influence of some non-ideal factors on sensitivity scaling. This work is significant in the field of atom-based quantum precision measurements.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":null,"pages":null},"PeriodicalIF":5.3,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00198-7","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134795368","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Demonstration of a switched CV-QKD network","authors":"Hans H. Brunner,&nbsp;Chi-Hang Fred Fung,&nbsp;Momtchil Peev,&nbsp;Rubén B. Méndez,&nbsp;Laura Ortiz,&nbsp;Juan P. Brito,&nbsp;Vicente Martín,&nbsp;José M. Rivas-Moscoso,&nbsp;Felipe Jiménez,&nbsp;Antonio A. Pastor,&nbsp;Diego R. López","doi":"10.1140/epjqt/s40507-023-00194-x","DOIUrl":"10.1140/epjqt/s40507-023-00194-x","url":null,"abstract":"<div><p>A quantum channel is a physical media able to carry quantum signals. Quantum key distribution (QKD) requires direct quantum channels between every pair of prepare-and-measure modules. This requirement heavily compromises the scalability of networks of directly connected QKD modules. A way to avoid this problem is to introduce switches that can dynamically reconfigure the set of connections. The reconfiguration of a quantum channel implies that the modules using it can adapt to the new channel and peer.</p><p>The maturity and flexibility of continuous-variable QKD (CV-QKD) qualifies it as a strong contender for integration into optical communication networks. Here we present the implementation of a switched CV-QKD network embedded in the Madrid quantum testbed. The optical switching of the quantum paths significantly reduces the amount of required QKD modules and facilitates the scalability of the network. This demonstration highlights the flexibility and ease of integration of this emerging technology.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":null,"pages":null},"PeriodicalIF":5.3,"publicationDate":"2023-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00194-x","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134797249","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A stochastic evaluation of quantum Fisher information matrix with generic Hamiltonians","authors":"Le Bin Ho","doi":"10.1140/epjqt/s40507-023-00195-w","DOIUrl":"10.1140/epjqt/s40507-023-00195-w","url":null,"abstract":"<div><p>Quantum Fisher information matrix (QFIM) is a fundamental quantity in quantum physics, which closely links to diverse fields such as quantum metrology, phase transitions, entanglement witness, and quantum speed limit. It is crucial in quantum parameter estimation, central to the ultimate Cramér-Rao bound. Recently, the evaluation of QFIM using quantum circuit algorithms has been proposed for systems with multiplicative parameters Hamiltonian. However, systems with generic Hamiltonians still lack these proposed schemes. This work introduces a quantum-circuit-based approach for evaluating QFIM with generic Hamiltonians. We present a time-dependent stochastic parameter-shift rule for the derivatives of evolved quantum states, whereby the QFIM can be obtained. The scheme can be executed in universal quantum computers under the family of parameterized gates. In magnetic field estimations, we demonstrate the consistency between the results obtained from the stochastic parameter-shift rule and the exact results, while the results obtained from a standard parameter-shift rule slightly deviate from the exact ones. Our work sheds new light on studying QFIM with generic Hamiltonians using quantum circuit algorithms.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":null,"pages":null},"PeriodicalIF":5.3,"publicationDate":"2023-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00195-w","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134797262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}