• npj Quantum Inform. (IF 7.286) Pub Date : 2021-01-04
Daniele Dequal; Luis Trigo Vidarte; Victor Roman Rodriguez; Giuseppe Vallone; Paolo Villoresi; Anthony Leverrier; Eleni Diamanti

Establishing secure communication links at a global scale is a major potential application of quantum information science but also extremely challenging for the underlying technology. Although milestone experiments using satellite-to-ground links and exploiting singe-photon encoding for implementing quantum key distribution have shown recently that this goal is achievable, it is still necessary to

更新日期：2021-01-04
• npj Quantum Inform. (IF 7.286) Pub Date : 2021-01-04
A. V. Andreev; A. G. Balanov; T. M. Fromhold; M. T. Greenaway; A. E. Hramov; W. Li; V. V. Makarov; A. M. Zagoskin

Progress in the creation of large-scale, artificial quantum coherent structures demands the investigation of their nonequilibrium dynamics when strong interactions, even between remote parts, are non-perturbative. Analysis of multiparticle quantum correlations in a large system in the presence of decoherence and external driving is especially topical. Still, the scaling behavior of dynamics and related

更新日期：2021-01-04
• npj Quantum Inform. (IF 7.286) Pub Date : 2021-01-04
Sumeet Khatri; Anthony J. Brady; Renée A. Desporte; Manon P. Bart; Jonathan P. Dowling

Recent experimental breakthroughs in satellite quantum communications have opened up the possibility of creating a global quantum internet using satellite links. This approach appears to be particularly viable in the near term, due to the lower attenuation of optical signals from satellite to ground, and due to the currently short coherence times of quantum memories. The latter prevents ground-based

更新日期：2021-01-04
• npj Quantum Inform. (IF 7.286) Pub Date : 2021-01-04
K. C. Chen; E. Bersin; D. Englund

We propose an integrated photonics device for mapping qubits encoded in the polarization of a photon onto the spin state of a solid-state defect coupled to a photonic crystal cavity: a “polarization-encoded photon-to-spin interface” (PEPSI). We perform a theoretical analysis of the state fidelity’s dependence on the device’s polarization extinction ratio and atom–cavity cooperativity. Furthermore,

更新日期：2021-01-04
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-12-18
Darius Bunandar; Luke C. G. Govia; Hari Krovi; Dirk Englund

Quantum key distribution (QKD) allows for secure communications safe against attacks by quantum computers. QKD protocols are performed by sending a sizeable, but finite, number of quantum signals between the distant parties involved. Many QKD experiments, however, predict their achievable key rates using asymptotic formulas, which assume the transmission of an infinite number of signals, partly because

更新日期：2020-12-18
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-12-15
Wen-Hao Zhang; Xiao Liu; Peng Yin; Xing-Xiang Peng; Gong-Chu Li; Xiao-Ye Xu; Shang Yu; Zhi-Bo Hou; Yong-Jian Han; Jin-Shi Xu; Zong-Quan Zhou; Geng Chen; Chuan-Feng Li; Guang-Can Guo

Quantum state verification provides an efficient approach to characterize the reliability of quantum devices for generating certain target states. The figure of merit of a specific strategy is the estimated infidelity ϵ of the tested state to the target state, given a certain number of performed measurements n. Entangled measurements constitute the globally optimal strategy and achieve the scaling

更新日期：2020-12-15
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-12-14
Boris Mihailov Varbanov; Francesco Battistel; Brian Michael Tarasinski; Viacheslav Petrovych Ostroukh; Thomas Eugene O’Brien; Leonardo DiCarlo; Barbara Maria Terhal

Leakage outside of the qubit computational subspace, present in many leading experimental platforms, constitutes a threatening error for quantum error correction (QEC) for qubits. We develop a leakage-detection scheme via Hidden Markov models (HMMs) for transmon-based implementations of the surface code. By performing realistic density-matrix simulations of the distance-3 surface code (Surface-17)

更新日期：2020-12-14
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-12-11
Lukas Martinetz; Klaus Hornberger; James Millen; M. S. Kim; Benjamin A. Stickler

Preparing and observing quantum states of nanoscale particles is a challenging task with great relevance for quantum technologies and tests of fundamental physics. In contrast to atomic systems with discrete transitions, nanoparticles exhibit a practically continuous absorption spectrum and thus their quantum dynamics cannot be easily manipulated. Here, we demonstrate that charged nanoscale dielectrics

更新日期：2020-12-13
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-12-10
Xing Lin; Shuang Wang; Zhen-Qiang Yin; Guan-Jie Fan-Yuan; Rong Wang; Wei Chen; De-Yong He; Zheng Zhou; Guang-Can Guo; Zheng-Fu Han

A quantum random number generator (QRNG) as a genuine source of randomness is essential in many applications, such as number simulation and cryptography. Recently, a source-independent quantum random number generator (SI-QRNG), which can generate secure random numbers with untrusted sources, has been realized. However, the measurement loopholes of the trusted but imperfect devices used in SI-QRNGs

更新日期：2020-12-10
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-12-07
Ming Gong; Feihu Xu; Zheng-Da Li; Zizhu Wang; Yu-Zhe Zhang; Yulin Wu; Shaowei Li; Youwei Zhao; Shiyu Wang; Chen Zha; Hui Deng; Zhiguang Yan; Hao Rong; Futian Liang; Jin Lin; Yu Xu; Cheng Guo; Lihua Sun; Anthony D. Castellano; Cheng-Zhi Peng; Yu-Ao Chen; Xiaobo Zhu; Jian-Wei Pan

Quantum resetting protocols allow a quantum system to be sent to a state in the past by making it interact with quantum probes when neither the free evolution of the system nor the interaction is controlled. We experimentally verify the simplest non-trivial case of a quantum resetting protocol, known as the $${{\mathcal{W}}}_{4}$$ protocol, with five superconducting qubits, testing it with different

更新日期：2020-12-07
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-12-04
Lorenzo Leandro; Jacob Hastrup; Rodion Reznik; George Cirlin; Nika Akopian

GaAs quantum dots in nanowires are one of the most promising candidates for scalable quantum photonics. They have excellent optical properties, can be frequency-tuned to atomic transitions, and offer a robust platform for fabrication of multi-qubit devices that promise to unlock the full technological potential of quantum dots. Coherent resonant excitation is necessary for virtually any practical application

更新日期：2020-12-04
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-12-04
Huan-Yu Ku; Neill Lambert; Feng-Jui Chan; Clive Emary; Yueh-Nan Chen; Franco Nori

The Leggett–Garg inequality attempts to classify experimental outcomes as arising from one of two possible classes of physical theories: those described by macrorealism (which obey our intuition about how the macroscopic classical world behaves) and those that are not (e.g., quantum theory). The development of cloud-based quantum computing devices enables us to explore the limits of macrorealism. In

更新日期：2020-12-04
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-12-04
Bienvenu Ndagano; Hugo Defienne; Ashley Lyons; Ilya Starshynov; Federica Villa; Simone Tisa; Daniele Faccio

Spatial correlations between two photons are the key resource in realising many quantum imaging schemes. Measurement of the bi-photon correlation map is typically performed using single-point scanning detectors or single-photon cameras based on charged coupled device (CCD) technology. However, both approaches are limited in speed due to the slow scanning and the low frame rate of CCD-based cameras

更新日期：2020-12-04
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-12-04
Alessio Belenchia; Luca Mancino; Gabriel T. Landi; Mauro Paternostro

The entropy production rate is a key quantity in nonequilibrium thermodynamics of both classical and quantum processes. No universal theory of entropy production is available to date, which hinders progress toward its full grasping. By using a phase space-based approach, here we take the current framework for the assessment of thermodynamic irreversibility all the way to quantum regimes by characterizing

更新日期：2020-12-04
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-12-04
V. Cimini; S. Gherardini; M. Barbieri; I. Gianani; M. Sbroscia; L. Buffoni; M. Paternostro; F. Caruso

We characterize the energetic footprint of a two-qubit quantum gate from the perspective of non-equilibrium quantum thermodynamics. We experimentally reconstruct the statistics of energy and entropy fluctuations following the implementation of a controlled-unitary gate, linking them to the performance of the gate itself and the phenomenology of Landauer’s principle at the single-quantum level. Our

更新日期：2020-12-04
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-12-04
Akram Youssry; Gerardo A. Paz-Silva; Christopher Ferrie

The ability to use quantum technology to achieve useful tasks, be they scientific or industry related, boils down to precise quantum control. In general it is difficult to assess a proposed solution due to the difficulties in characterizing the quantum system or device. These arise because of the impossibility to characterize certain components in situ, and are exacerbated by noise induced by the environment

更新日期：2020-12-04
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-12-02
Mauro Valeri; Emanuele Polino; Davide Poderini; Ilaria Gianani; Giacomo Corrielli; Andrea Crespi; Roberto Osellame; Nicolò Spagnolo; Fabio Sciarrino

Achieving ultimate bounds in estimation processes is the main objective of quantum metrology. In this context, several problems require measurement of multiple parameters by employing only a limited amount of resources. To this end, adaptive protocols, exploiting additional control parameters, provide a tool to optimize the performance of a quantum sensor to work in such limited data regime. Finding

更新日期：2020-12-02
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-10-27
Christopher Chamberland; Kyungjoo Noh

Fault-tolerant quantum computing promises significant computational speedup over classical computing for a variety of important problems. One of the biggest challenges for realizing fault-tolerant quantum computing is preparing magic states with sufficiently low error rates. Magic state distillation is one of the most efficient schemes for preparing high-quality magic states. However, since magic state

更新日期：2020-10-28
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-10-27
Xinhe Jiang; Kun Wang; Kaiyi Qian; Zhaozhong Chen; Zhiyu Chen; Liangliang Lu; Lijun Xia; Fangmin Song; Shining Zhu; Xiaosong Ma

Quantum devices for generating entangled states have been extensively studied and widely used. As so, it becomes necessary to verify that these devices truly work reliably and efficiently as they are specified. Here we experimentally realize the recently proposed two-qubit entangled state verification strategies using both local measurements (nonadaptive) and active feed-forward operations (adaptive)

更新日期：2020-10-28
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-10-23
G. S. Thekkadath; M. E. Mycroft; B. A. Bell; C. G. Wade; A. Eckstein; D. S. Phillips; R. B. Patel; A. Buraczewski; A. E. Lita; T. Gerrits; S. W. Nam; M. Stobińska; A. I. Lvovsky; I. A. Walmsley

Quantum phenomena such as entanglement can improve fundamental limits on the sensitivity of a measurement probe. In optical interferometry, a probe consisting of N entangled photons provides up to a $$\sqrt{N}$$ enhancement in phase sensitivity compared to a classical probe of the same energy. Here, we employ high-gain parametric down-conversion sources and photon-number-resolving detectors to perform

更新日期：2020-10-28
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-10-21
Xiao-Min Hu; Wen-Bo Xing; Chao Zhang; Bi-Heng Liu; Matej Pivoluska; Marcus Huber; Yun-Feng Huang; Chuan-Feng Li; Guang-Can Guo

Quantum entanglement is one of the most important resources in quantum information. In recent years, the research of quantum entanglement mainly focused on the increase in the number of entangled qubits or the high-dimensional entanglement of two particles. Compared with qubit states, multipartite high-dimensional entangled states have beneficial properties and are powerful for constructing quantum

更新日期：2020-10-28
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-10-16
Xingze Qiu; Jie Zou; Xiaodong Qi; Xiaopeng Li

We present an efficient approach to precisely simulate tight binding models with optical lattices, based on programmable digital-micromirror-device (DMD) techniques. Our approach consists of a subroutine of Wegner-flow enabled precise extraction of a tight-binding model for a given optical potential, and a reverse engineering step of adjusting the potential for a targeting model, for both of which

更新日期：2020-10-17
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-10-15
Stefan Langenfeld; Olivier Morin; Matthias Körber; Gerhard Rempe

Photonic qubits memories are essential ingredients of numerous quantum networking protocols. The ideal situation features quantum computing nodes that are efficiently connected to quantum communication channels via quantum interfaces. The nodes contain a set of long-lived matter qubits, the channels support the propagation of light qubits, and the interface couples light and matter qubits. Toward this

更新日期：2020-10-16
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-09-25
Song Li; Jyh-Pin Chou; Alice Hu; Martin B. Plenio; Péter Udvarhelyi; Gergő Thiering; Mehdi Abdi; Adam Gali

We study the effect of strain on the physical properties of the nitrogen antisite-vacancy pair in hexagonal boron nitride (h-BN), a color center that may be employed as a quantum bit in a two-dimensional material. With group theory and ab initio analysis we show that strong electron–phonon coupling plays a key role in the optical activation of this color center. We find a giant shift on the zero-phonon-line

更新日期：2020-09-25
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-09-25
Benjamin Nachman; Miroslav Urbanek; Wibe A. de Jong; Christian W. Bauer

In the current era of noisy intermediate-scale quantum computers, noisy qubits can result in biased results for early quantum algorithm applications. This is a significant challenge for interpreting results from quantum computer simulations for quantum chemistry, nuclear physics, high energy physics (HEP), and other emerging scientific applications. An important class of qubit errors are readout errors

更新日期：2020-09-25
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-09-18
Cristina Cîrstoiu; Zoë Holmes; Joseph Iosue; Lukasz Cincio; Patrick J. Coles; Andrew Sornborger

Trotterization-based, iterative approaches to quantum simulation (QS) are restricted to simulation times less than the coherence time of the quantum computer (QC), which limits their utility in the near term. Here, we present a hybrid quantum-classical algorithm, called variational fast forwarding (VFF), for decreasing the quantum circuit depth of QSs. VFF seeks an approximate diagonalization of a

更新日期：2020-09-20
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-09-18
E. R. MacQuarrie; Samuel F. Neyens; J. P. Dodson; J. Corrigan; Brandur Thorgrimsson; Nathan Holman; M. Palma; L. F. Edge; Mark Friesen; S. N. Coppersmith; M. A. Eriksson

Fast operations, an easily tunable Hamiltonian, and a straightforward two-qubit interaction make charge qubits a useful tool for benchmarking device performance and exploring two-qubit dynamics. Here, we tune a linear chain of four Si/SiGe quantum dots to host two double dot charge qubits. Using the capacitance between the double dots to mediate a strong two-qubit interaction, we simultaneously drive

更新日期：2020-09-20
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-09-18
D. Cohen; T. Gefen; L. Ortiz; A. Retzker

The ultimate precision limit in estimating the Larmor frequency of N unentangled qubits is well established, and is highly important for magnetometers, gyroscopes, and other types of quantum sensors. However, this limit assumes perfect projective measurements of the quantum registers. This requirement is not practical in many physical systems, such as NMR spectroscopy, where a weakly interacting external

更新日期：2020-09-20
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-09-17
Daniil M. Lukin; Alexander D. White; Rahul Trivedi; Melissa A. Guidry; Naoya Morioka; Charles Babin; Öney O. Soykal; Jawad Ul-Hassan; Nguyen Tien Son; Takeshi Ohshima; Praful K. Vasireddy; Mamdouh H. Nasr; Shuo Sun; Jean-Philippe W. MacLean; Constantin Dory; Emilio A. Nanni; Jörg Wrachtrup; Florian Kaiser; Jelena Vučković

The ability to shape photon emission facilitates strong photon-mediated interactions between disparate physical systems, thereby enabling applications in quantum information processing, simulation and communication. Spectral control in solid state platforms such as color centers, rare earth ions, and quantum dots is particularly attractive for realizing such applications on-chip. Here we propose the

更新日期：2020-09-18
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-09-16
Xi Kong; Leixin Zhou; Zhijie Li; Zhiping Yang; Bensheng Qiu; Xiaodong Wu; Fazhan Shi; Jiangfeng Du

Two-dimensional nuclear magnetic resonance (NMR) is indispensable to molecule structure determination. Nitrogen-vacancy center in diamond has been proposed and developed as an outstanding quantum sensor to realize NMR in nanoscale or even single molecule. However, like conventional multi-dimensional NMR, a more efficient data accumulation and processing method is necessary to realize applicable two-dimensional

更新日期：2020-09-16
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-09-08
Yuan-Yuan Zhao; Huan-Yu Ku; Shin-Liang Chen; Hong-Bin Chen; Franco Nori; Guo-Yong Xiang; Chuan-Feng Li; Guang-Can Guo; Yueh-Nan Chen

Within the framework of quantum refereed steering games, quantum steerability can be certified without any assumption on the underlying state nor the measurements involved. Such a scheme is termed the measurement-device-independent (MDI) scenario. Here, we introduce a measure of steerability in an MDI scenario, i.e., the result merely depends on the observed statistics and the quantum inputs. We prove

更新日期：2020-09-09
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-09-08
Xiaoche Wang; Yuxuan Xiao; Chuanpu Liu; Eric Lee-Wong; Nathan J. McLaughlin; Hanfeng Wang; Mingzhong Wu; Hailong Wang; Eric E. Fullerton; Chunhui Rita Du

Nitrogen vacancy (NV) centers, optically active atomic defects in diamond, have attracted tremendous interest for quantum sensing, network, and computing applications due to their excellent quantum coherence and remarkable versatility in a real, ambient environment. One of the critical challenges to develop NV-based quantum operation platforms results from the difficulty in locally addressing the quantum

更新日期：2020-09-09
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-09-03
Li-Ping Yang; Zubin Jacob

The temporal dynamics of large quantum systems perturbed weakly by a single excitation can give rise to unique phenomena at the quantum phase boundaries. Here, we develop a time-dependent model to study the temporal dynamics of a single photon interacting with a defect within a large system of interacting spin qubits (N > 100). Our model predicts a quantum resource, giant susceptibility, when the system

更新日期：2020-09-03
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-09-02
Man-Hong Yung; Fei Meng; Xiao-Ming Zhang; Ming-Jing Zhao

To detect a stealth target, one may directly probe it with a single photon and analyze the reflected signals. The efficiency of such conventional detection scheme can potentially be enhanced by quantum illumination, where entanglement is exploited to break the classical limits. The question is what is the optimal signal state for achieving the detection limit? Here, we address this question in a general

更新日期：2020-09-02
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-08-27
Gavin McCauley; Benjamin Cruikshank; Denys I. Bondar; Kurt Jacobs

Realistic models of quantum systems must include dissipative interactions with a thermal environment. For weakly-damped systems, while the Lindblad-form Markovian master equation is invaluable for this task, it applies only when the frequencies of any subset of the system’s transitions are degenerate, or their differences are much greater than the transitions’ linewidths. Outside of these regimes the

更新日期：2020-08-27
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-08-26
Chang-Kang Hu; Alan C. Santos; Jin-Ming Cui; Yun-Feng Huang; Diogo O. Soares-Pinto; Marcelo S. Sarandy; Chuan-Feng Li; Guang-Can Guo

Quantum thermodynamics aims at investigating both the emergence and the limits of the laws of thermodynamics from a quantum mechanical microscopic approach. In this scenario, thermodynamic processes with no heat exchange, namely, adiabatic transformations, can be implemented through quantum evolutions in closed systems, even though the notion of a closed system is always an idealization and approximation

更新日期：2020-08-26
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-08-24
Ming-Xin Dong; Dong-Sheng Ding; Yi-Chen Yu; Ying-Hao Ye; Wei-Hang Zhang; En-Ze Li; Lei Zeng; Kan Zhang; Da-Chuang Li; Guang-Can Guo; Bao-Sen Shi

Nowadays the most intriguing features of wave-particle complementarity of single-photons are exemplified by the famous Wheeler’s delayed-choice experiment with linear optics, nuclear magnetic resonance, and integrated photonic device systems in the optical platform. Until now, the delayed-choice experiments are demonstrated by either massless photons or massive particles, such as atoms, however, there

更新日期：2020-08-24
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-08-21
Diego Ristè; Luke C. G. Govia; Brian Donovan; Spencer D. Fallek; William D. Kalfus; Markus Brink; Nicholas T. Bronn; Thomas A. Ohki

Although qubit coherence times and gate fidelities are continuously improving, logical encoding is essential to achieve fault tolerance in quantum computing. In most encoding schemes, correcting or tracking errors throughout the computation is necessary to implement a universal gate set without adding significant delays in the processor. Here, we realize a classical control architecture for the fast

更新日期：2020-08-21
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-08-21
Tamás Kriváchy; Yu Cai; Daniel Cavalcanti; Arash Tavakoli; Nicolas Gisin; Nicolas Brunner

Characterizing quantum nonlocality in networks is a challenging, but important problem. Using quantum sources one can achieve distributions which are unattainable classically. A key point in investigations is to decide whether an observed probability distribution can be reproduced using only classical resources. This causal inference task is challenging even for simple networks, both analytically and

更新日期：2020-08-21
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-08-07
Claudio Bonizzoni; Alberto Ghirri; Fabio Santanni; Matteo Atzori; Lorenzo Sorace; Roberta Sessoli; Marco Affronte

Hybrid architectures combining complementary quantum systems will be largely used in quantum technologies and the integration of different components is one of the key issues. Thanks to their long coherence times and the easy manipulation with microwave pulses, electron spins hold a potential for the realization of quantum memories. Here, we test diluted oxovanadium tetraphenyl porphyrin (VO(TPP))

更新日期：2020-08-08
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-08-06
Tom Struck; Arne Hollmann; Floyd Schauer; Olexiy Fedorets; Andreas Schmidbauer; Kentarou Sawano; Helge Riemann; Nikolay V. Abrosimov; Łukasz Cywiński; Dominique Bougeard; Lars R. Schreiber

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

更新日期：2020-08-06
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-08-06
Roberto Stassi; Mauro Cirio; Franco Nori

So far, superconducting quantum computers have certain constraints on qubit connectivity, such as nearest-neighbor couplings. To overcome this limitation, we propose a scalable architecture to simultaneously connect several pairs of distant qubits via a dispersively coupled quantum bus. The building block of the bus is composed of orthogonal coplanar waveguide resonators connected through ancillary

更新日期：2020-08-06
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-08-03
Han Liu; Amr S. Helmy

We propose, analyze, and evaluate a technique for the joint measurement of time–frequency entanglement between two photons. In particular, we show that the frequency sum and time difference of two photons could be simultaneously measured through the sum-frequency generation process, without measuring the time or frequency of each individual photon. We demonstrate the usefulness of this technique by

更新日期：2020-08-03
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-07-29
Wonjin Jang; Jehyun Kim; Min-Kyun Cho; Hwanchul Chung; Sanghyeok Park; Jaeun Eom; Vladimir Umansky; Yunchul Chung; Dohun Kim

Fast and high-fidelity quantum state detection is essential for building robust spin-based quantum information processing platforms in semiconductors. The Pauli spin blockade (PSB)-based spin-to-charge conversion and its variants are widely used for the spin state discrimination of two-electron singlet–triplet (ST0) qubits; however, the single-shot measurement fidelity is limited by either the low

更新日期：2020-07-29
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-07-28
Adam Pearson; Anurag Mishra; Itay Hen; Daniel A. Lidar

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

更新日期：2020-07-28
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-07-17
Kübra Yeter-Aydeniz; Raphael C. Pooser; George Siopsis

Various methods have been developed for the quantum computation of the ground and excited states of physical and chemical systems, but many of them require either large numbers of ancilla qubits or high-dimensional optimization in the presence of noise. The quantum imaginary-time evolution (QITE) and quantum Lanczos (QLanczos) methods proposed in Motta et al. (2020) eschew the aforementioned issues

更新日期：2020-07-17
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-07-16
Frank Gaitan

There is great interest in using quantum computers to efficiently simulate a quantum system’s dynamics as existing classical computers cannot do this. Little attention, however, has been given to quantum simulation of a classical nonlinear continuum system such as a viscous fluid even though this too is hard for classical computers. Such fluids obey the Navier–Stokes nonlinear partial differential

更新日期：2020-07-16
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-07-16
Xiaodong Yang; Jayne Thompson; Ze Wu; Mile Gu; Xinhua Peng; Jiangfeng Du

Experimentally achieving the precision that standard quantum metrology schemes promise is always challenging. Recently, additional controls were applied to design feasible quantum metrology schemes. However, these approaches generally does not consider ease of implementation, raising technological barriers impeding its realization. In this paper, we circumvent this problem by applying closed-loop learning

更新日期：2020-07-16
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-07-08
Brian Coyle; Daniel Mills; Vincent Danos; Elham Kashefi

The search for an application of near-term quantum devices is widespread. Quantum machine learning is touted as a potential utilisation of such devices, particularly those out of reach of the simulation capabilities of classical computers. In this work, we study such an application in generative modelling, focussing on a class of quantum circuits known as Born machines. Specifically, we define a subset

更新日期：2020-07-08
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-07-03
D. R. W. Yost; M. E. Schwartz; J. Mallek; D. Rosenberg; C. Stull; J. L. Yoder; G. Calusine; M. Cook; R. Das; A. L. Day; E. B. Golden; D. K. Kim; A. Melville; B. M. Niedzielski; W. Woods; A. J. Kerman; W. D. Oliver

As superconducting qubit circuits become more complex, addressing a large array of qubits becomes a challenging engineering problem. Dense arrays of qubits benefit from, and may require, access via the third dimension to alleviate interconnect crowding. Through-silicon vias (TSVs) represent a promising approach to three-dimensional (3D) integration in superconducting qubit arrays—provided they are

更新日期：2020-07-03
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-06-26
Yariv Yanay; Jochen Braumüller; Simon Gustavsson; William D. Oliver; Charles Tahan

The pursuit of superconducting-based quantum computers has advanced the fabrication of and experimentation with custom lattices of qubits and resonators. Here, we describe a roadmap to use present experimental capabilities to simulate an interacting many-body system of bosons and measure quantities that are exponentially difficult to calculate numerically. We focus on the two-dimensional hard-core

更新日期：2020-06-26
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-06-25
M. Kristen; A. Schneider; A. Stehli; T. Wolz; S. Danilin; H. S. Ku; J. Long; X. Wu; R. Lake; D. P. Pappas; A. V. Ustinov; M. Weides

Experiments with superconducting circuits require careful calibration of the applied pulses and fields over a large frequency range. This remains an ongoing challenge as commercial semiconductor electronics are not able to probe signals arriving at the chip due to its cryogenic environment. Here, we demonstrate how the on-chip amplitude and frequency of a microwave signal can be inferred from the ac

更新日期：2020-06-25
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-06-19
Kang-Da Wu; Zhibo Hou; Guo-Yong Xiang; Chuan-Feng Li; Guang-Can Guo; Daoyi Dong; Franco Nori

The dynamics of open quantum systems and manipulation of quantum resources are both of fundamental interest in quantum physics. Here, we investigate the relation between quantum Markovianity and coherence, providing an effective way for detecting non-Markovianity based on the quantum-incoherent relative entropy of coherence ($${\mathcal{Q}}{\mathcal{I}}$$ REC). We theoretically show the relation between

更新日期：2020-06-19
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-06-19
Ikko Hamamura; Takashi Imamichi

The advent of cloud quantum computing has led to the rapid development of quantum algorithms. In particular, it is necessary to study variational quantum-classical hybrid algorithms, which are executable on noisy intermediate-scale quantum (NISQ) computers. Evaluations of observables appear frequently in the variational quantum-classical hybrid algorithms for NISQ computers. By speeding up the evaluation

更新日期：2020-06-19
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-06-17
Yibo Wang; Sayali Shevate; Tobias Martin Wintermantel; Manuel Morgado; Graham Lochead; Shannon Whitlock

We present programmable two-dimensional arrays of microscopic atomic ensembles consisting of more than 400 sites with nearly uniform filling and small atom number fluctuations. Our approach involves direct projection of light patterns from a digital micromirror device with high spatial resolution onto an optical pancake trap acting as a reservoir. This makes it possible to load large arrays of tweezers

更新日期：2020-06-17
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-06-12
Riddhi Swaroop Gupta; Claire L. Edmunds; Alistair R. Milne; Cornelius Hempel; Michael J. Biercuk

New quantum computing architectures consider integrating qubits as sensors to provide actionable information useful for calibration or decoherence mitigation on neighboring data qubits, but little work has addressed how such schemes may be efficiently implemented in order to maximize information utilization. Techniques from classical estimation and dynamic control, suitably adapted to the strictures

更新日期：2020-06-12
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-06-11
Yu Guo; Bai-Chu Yu; Xiao-Min Hu; Bi-Heng Liu; Yu-Chun Wu; Yun-Feng Huang; Chuan-Feng Li; Guang-Can Guo

The certification of entanglement dimensionality is of great importance in characterizing quantum systems. Recently, it was pointed out that quantum correlation of high-dimensional states can be simulated with a sequence of lower-dimensional states. Such a problem may render existing characterization protocols unreliable—the observed entanglement may not be a truly high-dimensional one. Here, we introduce

更新日期：2020-06-11
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-06-09
Lukas Knips; Jan Dziewior; Waldemar Kłobus; Wiesław Laskowski; Tomasz Paterek; Peter J. Shadbolt; Harald Weinfurter; Jasmin D. A. Meinecke

Quantum entanglement is usually revealed via a well aligned, carefully chosen set of measurements. Yet, under a number of experimental conditions, for example in communication within multiparty quantum networks, noise along the channels or fluctuating orientations of reference frames may ruin the quality of the distributed states. Here, we show that even for strong fluctuations one can still gain detailed

更新日期：2020-06-09
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-06-02
Sebastian Knauer; John P. Hadden; John G. Rarity

Diamond has established itself as an ideal material for photonics and optomechanics, due to its broad-band transparency and hardness. In addition, colour centres hosted within its lattice such as the nitrogen-vacancy (NV) centre, have become leading candidates for use in quantum information processing, and quantum sensors. The fabrication of nanoscale devices coupled to high quality NVs has been an

更新日期：2020-06-02
• npj Quantum Inform. (IF 7.286) Pub Date : 2020-06-02
Nicolas P. D. Sawaya; Tim Menke; Thi Ha Kyaw; Sonika Johri; Alán Aspuru-Guzik; Gian Giacomo Guerreschi

Simulation of quantum systems is expected to be one of the most important applications of quantum computing, with much of the theoretical work so far having focused on fermionic and spin-$$\frac{1}{2}$$ systems. Here, we instead consider encodings of d-level (i.e., qudit) quantum operators into multi-qubit operators, studying resource requirements for approximating operator exponentials by Trotterization

更新日期：2020-06-02
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