EPJ Quantum Technology最新文献

{"title":"Vector—towards quantum key distribution with small satellites","authors":"Alexander V. Miller,&nbsp;Liubov V. Pismeniuk,&nbsp;Alexey V. Duplinsky,&nbsp;Vitaly E. Merzlinkin,&nbsp;Aleksandr A. Plukchi,&nbsp;Kseniia A. Tikhonova,&nbsp;Ivan S. Nesterov,&nbsp;Dmitry O. Sevryukov,&nbsp;Sergey D. Levashov,&nbsp;Vladimir V. Fetisov,&nbsp;Sergei V. Krasnopejev,&nbsp;Ruslan M. Bakhshaliev","doi":"10.1140/epjqt/s40507-023-00208-8","DOIUrl":"10.1140/epjqt/s40507-023-00208-8","url":null,"abstract":"<div><p>A satellite-constellation based global quantum network could allow secure quantum communication between remote users worldwide. Such a constellation could be formed of micro- or even nanosatellites, which have the advantage of being more cost-effective than larger expensive spacecrafts. At the same time, the features of quantum communication impose a number of technical requirements that are more difficult to meet when using small satellites. Full-fledged quantum communication has been demonstrated with neither a micro- nor a nanosatellite so far. The authors took up this challenge and have developed a 6U CubeSat weighting 9.5 kg. The satellite is to be launched in 2023 and has already successfully passed all the pre-flight tests. The mission is not yet intended for fully quantum communication. Nevertheless, the authors are testing such key functional elements as polarization reference-frame synchronization and acquisition, pointing and tracking system on it. Besides that, the payload accommodates a full-duplex telecommunication system operating at a bit rate of 50 Mbit/s: an up- and a downlink at wavelengths of 808 and 850 nm. After the satellite is launched, the main goal to be achieved is to demonstrate stable connection between it and an optical ground station and carry out multiple communication sessions. In quantum communication, generating secret keys from raw measurement data implies two-way exchange of significant amount of information and therefore availability of a classical communication channel with a high bandwidth is one of the crucial things. In the following mission, which envisages an overall quantum key distribution system, we plan to use the free-space optical link for such an exchange of data, whereas the RF link will only be used for telemetry and telecommand.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"10 1","pages":""},"PeriodicalIF":5.3,"publicationDate":"2023-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00208-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138454572","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 75 km-fiber quantum clock synchronization in quantum entanglement distribution network","authors":"Bang-Ying Tang,&nbsp;Ming Tian,&nbsp;Huan Chen,&nbsp;Hui Han,&nbsp;Han Zhou,&nbsp;Si-Chen Li,&nbsp;Bo Xu,&nbsp;Rui-Fang Dong,&nbsp;Bo Liu,&nbsp;Wan-Rong Yu","doi":"10.1140/epjqt/s40507-023-00207-9","DOIUrl":"10.1140/epjqt/s40507-023-00207-9","url":null,"abstract":"<div><p>The quantum entanglement distribution network, serviced as the communication infrastructure which distributes quantum information among remote users, enables many applications beyond the reach of classical networks. Recently, the applications such as quantum key distribution and quantum secure direct communication, have been successfully demonstrated in the quantum entanglement distribution network. In this article, we propose a multi-user round-trip quantum clock synchronization (QCS) scheme in the quantum network, which can be implemented with one single entangled photon source located at the server. The server distributes the entangled photons to remote multiple users with the wavelength division multiplexing strategy, and each user feeds partial received photons back to the server. The clock difference between the server and each user is calculated from the one-way and round-trip propagation times, which are determined according to the time correlation of entangled photons. Afterwards, the demonstration has been conducted between the server and a user over a 75-km-long fiber link, where the measured clock difference uncertainty is 4.45 ps, and the time deviation is 426 fs with an average time of 4000 s. Furthermore, the proposed QCS scheme is linearly scalable to many users, with respect to user hardware and number of deployed fibers.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"10 1","pages":""},"PeriodicalIF":5.3,"publicationDate":"2023-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00207-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138431587","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":"Effect of external magnetic fields on practical quantum random number generator","authors":"Yuan-Hao Li,&nbsp;Yang-Yang Fei,&nbsp;Wei-Long Wang,&nbsp;Xiang-Dong Meng,&nbsp;Hong Wang,&nbsp;Qian-Heng Duan,&nbsp;Yu Han,&nbsp;Zhi Ma","doi":"10.1140/epjqt/s40507-023-00206-w","DOIUrl":"10.1140/epjqt/s40507-023-00206-w","url":null,"abstract":"<div><p>Quantum random number generator (QRNG) based on the inherent randomness of fundamental quantum processes can provide provable true random numbers which play an important role in many fields. However, the security of practical QRNGs is linked to the performance of realistic devices. In particular, devices based on the Faraday effect in a QRNG system may be affected by external magnetic fields, which will inevitably open a loophole that an eavesdropper can exploit to steal the information of generated random numbers. In this work, the effects of external magnetic fields on the security of practical QRNGs are analyzed. Taking the quantum phase fluctuation based QRNG with unbalanced Michelson interferometer as an example, we experimentally demonstrate the rotation angle of the Faraday rotation mirror (FRM) is influenced by external magnetic fields. Then, we develop a theoretical model between the rotation angle deviation of FRM and conditional min-entropy. Simulation results show that the imperfect FRM leads to a reduction in the variance of measured signal and extractable randomness. Furthermore, the impacts of practical sampling device on the extractable randomness are analyzed in the presence of imperfect FRM, which indicates suitable parameters of the sampling device can improve the security of practical QRNGs. Potential countermeasures are also proposed. Our work reveals that external magnetic fields should be carefully considered in the application of practical QRNGs.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"10 1","pages":""},"PeriodicalIF":5.3,"publicationDate":"2023-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00206-w","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138431523","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":"Mutual entity authentication of quantum key distribution network system using authentication qubits","authors":"Hojoong Park,&nbsp;Byung Kwon Park,&nbsp;Min Ki Woo,&nbsp;Min-Sung Kang,&nbsp;Ji-Woong Choi,&nbsp;Ju-Sung Kang,&nbsp;Yongjin Yeom,&nbsp;Sang-Wook Han","doi":"10.1140/epjqt/s40507-023-00205-x","DOIUrl":"10.1140/epjqt/s40507-023-00205-x","url":null,"abstract":"<div><p>Entity authentication is crucial for ensuring secure quantum communication as it helps confirm the identity of participants before transmitting any confidential information. We propose a practical entity authentication protocol for quantum key distribution (QKD) network systems that utilizes authentication qubits. In this protocol, authentication qubits that are encoded with pre-shared information are generated and exchanged to verify the legitimacy of each entity. By using the authentication qubit, participants can identify each other with enhanced security level through the quantum channel. The proposed protocol can be easily integrated with existing QKD systems without the need for additional hardware. In this study, we demonstrated the efficacy of the proposed scheme using a 1xN QKD network system and verified its stable operation over a deployed fiber network. Additionally, a security analysis of the proposed entity authentication protocol and architecture is provided.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"10 1","pages":""},"PeriodicalIF":5.3,"publicationDate":"2023-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00205-x","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134796313","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":"Determination of the number of shots for Grover’s search algorithm","authors":"Mathieu Kessler,&nbsp;Diego Alonso,&nbsp;Pedro Sánchez","doi":"10.1140/epjqt/s40507-023-00204-y","DOIUrl":"10.1140/epjqt/s40507-023-00204-y","url":null,"abstract":"<div><p>This paper focuses on Grover’s quantum search algorithm, which is of paramount importance as a masterpiece of Quantum Computing software. Given the inherent probabilistic nature of quantum computers, quantum programs based on Grover’s algorithm need to be run a number of times in order to generate a histogram of candidate values for solutions, which are then checked to identify the valid ones. In this paper, the distribution of the required number of shots to find all or a fraction of all the solutions to the Grover’s search problem is studied. Firstly, considering the similarity of the probability problem with the well-known coupon collector’s problem, two formulae are obtained from asymptotic results on the distribution of the required number of shots, as the number of problem solutions grows. These expressions allow to compute the number of shots required to ensure that, with probability <i>p</i>, all or a fraction of all the solutions are found. Secondly, the probability mass function of the required number of shots is derived, which serves as a benchmark to assess the validity of the asymptotic approximations derived previously. A comparison between the two approaches is presented and, as a result, a rule of thumb to decide under which circumstances employ one or the other is proposed.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"10 1","pages":""},"PeriodicalIF":5.3,"publicationDate":"2023-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://epjquantumtechnology.springeropen.com/counter/pdf/10.1140/epjqt/s40507-023-00204-y","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134795842","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":"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":"10 1","pages":""},"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":"10 1","pages":""},"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":"10 1","pages":""},"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":"10 1","pages":""},"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":"10 1","pages":""},"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}