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Dissipative stability and dynamical phase transition in two driven interacting qubits Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-03-26 K V Shulga
We examine a two-qubit system influenced by a time-periodic external field while interacting with a Markovian bath. This scenario significantly impacts the temporal coherence characteristics of the system. By solving the evolution equation for the density matrix operator, we determine the characteristic equilibration time and analyze the concurrence parameter-a key metric for quantifying entanglement
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Bulk-boundary correspondence in topological systems with the momentum dependent energy shift Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-03-22 Huan-Yu Wang, Zhen-Biao Yang, 0000-0002-1179-2061Wu-Ming Liu2
Bulk-boundary correspondence (BBC) remains the central topic in modern condensed matter physics and has received a boost of interest with the recent discovery of non-Hermitian skin effects. However, there still exist profound features of BBC that are beyond the existing framework. Here, we report the unexpected behavior of BBC when the Hamiltonian contains terms of the form d0(k)I , which serves as
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Near MDS and near quantum MDS codes via orthogonal arrays Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-03-22 Shanqi Pang, Chaomeng Zhang, Mengqian Chen, Miaomiao Zhang
Near maximum distance separable (NMDS) codes are closely related to interesting objects in finite geometry and have nice applications in combinatorics and cryptography. But there are many unsolved problems about construction of NMDS codes. In this paper, by using symmetrical orthogonal arrays (OAs), we construct a lot of NMDS, m-MDS and almost extremal NMDS codes. Quantum error-correcting codes (QECCs)
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Generating scalable graph states in an atom-nanophotonic interface Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-03-22 C-H Chien, S Goswami, C-C Wu, W-S Hiew, Y-C Chen, H H Jen
Scalable graph states are essential for measurement-based quantum computation and many entanglement-assisted applications in quantum technologies. Generation of these multipartite entangled states requires a controllable and efficient quantum device with delicate design of generation protocol. Here we propose to prepare high-fidelity and scalable graph states in one and two dimensions, which can be
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High flux strontium atom source Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-03-19 C-H Feng, P Robert, P Bouyer, B Canuel, J Li, S Das, C C Kwong, D Wilkowski, M Prevedelli, A Bertoldi
We present a novel cold strontium atom source designed for quantum sensors. We optimized the deceleration process to capture a large velocity class of atoms emitted from an oven and achieved a compact and low-power setup capable of generating a high atomic flux. Our approach involves velocity-dependent transverse capture of atoms using a two-dimensional magneto-optical trap. To enhance the atomic flux
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Avoiding barren plateaus in the variational determination of geometric entanglement Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-02-29 L Zambrano, A D Muñoz-Moller, M Muñoz, L Pereira, A Delgado
The barren plateau (BP) phenomenon is one of the main obstacles to implementing variational quantum algorithms in the current generation of quantum processors. Here, we introduce a method capable of avoiding the BP phenomenon in the variational determination of the geometric measure of entanglement for a large number of qubits. The method is based on measuring compatible two-qubit local functions whose
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Towards experimental classical verification of quantum computation Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-02-26 Roman Stricker, Jose Carrasco, Martin Ringbauer, Lukas Postler, Michael Meth, Claire Edmunds, Philipp Schindler, Rainer Blatt, Peter Zoller, Barbara Kraus, Thomas Monz
With today’s quantum processors venturing into regimes beyond the capabilities of classical devices, we face the challenge to verify that these devices perform as intended, even when we cannot check their results on classical computers. In a recent breakthrough in computer science, a protocol was developed that allows the verification of the output of a computation performed by an untrusted quantum
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Variational quantum algorithms for simulation of Lindblad dynamics Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-02-23 Tasneem M Watad, Netanel H Lindner
We introduce variational hybrid classical-quantum algorithms to simulate the Lindblad master equation and its adjoint for time-evolving Markovian open quantum systems and quantum observables. Our methods are based on a direct representation of density matrices and quantum observables as quantum superstates. We design and optimize low-depth variational quantum circuits that efficiently capture the unitary
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Experimental implementation of quantum-walk-based portfolio optimization Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-02-23 Dengke Qu, Edric Matwiejew, Kunkun Wang, Jingbo Wang, Peng Xue
The application of quantum algorithms has attracted much attention as it holds the promise of solving practical problems that are intractable to classical algorithms. One such application is the recent development of a quantum-walk-based optimization algorithm approach to portfolio optimization under the modern portfolio theory framework. In this paper, we demonstrate an experimental realization of
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Fast generation of spin squeezing via resonant spin-boson coupling Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-02-21 Diego Barberena, Sean R Muleady, John J Bollinger, Robert J Lewis-Swan, Ana Maria Rey
We propose protocols for the creation of useful entangled states in a system of spins collectively coupled to a bosonic mode, directly applicable to trapped-ion and cavity QED setups. The protocols use coherent manipulations of the resonant spin-boson interactions naturally arising in these systems to prepare spin squeezed states exponentially fast in time. The resonance condition harnesses the full
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Hybrid actor-critic algorithm for quantum reinforcement learning at CERN beam lines Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-02-21 Michael Schenk, Elías F Combarro, Michele Grossi, Verena Kain, Kevin Shing Bruce Li, Mircea-Marian Popa, Sofia Vallecorsa
Free energy-based reinforcement learning (FERL) with clamped quantum Boltzmann machines (QBM) was shown to significantly improve the learning efficiency compared to classical Q-learning with the restriction, however, to discrete state-action space environments. In this paper, the FERL approach is extended to multi-dimensional continuous state-action space environments to open the doors for a broader
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A thermodynamic approach to optimization in complex quantum systems Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-02-16 Alberto Imparato, Nicholas Chancellor, Gabriele De Chiara
We consider the problem of finding the energy minimum of a complex quantum Hamiltonian by employing a non-Markovian bath prepared in a low energy state. The energy minimization problem is thus turned into a thermodynamic cooling protocol in which we repeatedly put the system of interest in contact with a colder auxiliary system. By tuning the internal parameters of the bath, we show that the optimal
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An expressive ansatz for low-depth quantum approximate optimisation Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-02-13 V Vijendran, Aritra Das, Dax Enshan Koh, Syed M Assad, Ping Koy Lam
The quantum approximate optimisation algorithm (QAOA) is a hybrid quantum–classical algorithm used to approximately solve combinatorial optimisation problems. It involves multiple iterations of a parameterised ansatz that consists of a problem and mixer Hamiltonian, with the parameters being classically optimised. While QAOA can be implemented on near-term quantum hardware, physical limitations such
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Compilation of algorithm-specific graph states for quantum circuits Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-02-12 Madhav Krishnan Vijayan, Alexandru Paler, Jason Gavriel, Casey R Myers, Peter P Rohde, Simon J Devitt
We present a quantum circuit compiler that prepares an algorithm-specific graph state from quantum circuits described in high level languages, such as Cirq and Q#. The computation can then be implemented using a series of non-Pauli measurements on this graph state. By compiling the graph state directly instead of starting with a standard lattice cluster state and preparing it over the course of the
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Excitons guided by polaritons Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-02-12 K Mukherjee, S Wüster
We show that an exciton on a discrete chain of sites can be guided by effective measurements induced by an ambient, non-equilibrium medium that is synchronised to the exciton transport. For experimental verification, we propose a hybrid cold atom platform, carrying the exciton as electronic excitation on a chain of atoms, which are surrounded by a slow light medium supporting polaritons. The chain
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Low-complexity adaptive reconciliation protocol for continuous-variable quantum key distribution Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-02-08 Xue-Qin Jiang, Shengyuan Xue, Jiahao Tang, Peng Huang, Guihua Zeng
In continuous-variable quantum key distribution systems, reconciliation is a crucial step that significantly affects the secret key rate (SKR). The rateless protocol based on Raptor codes can achieve high reconciliation efficiency at low signal-to-noise ratios (SNRs). However, the high complexity of low-density parity-check (LDPC) codes used for the precoding in Raptor codes limits the speed of reconciliation
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Optimizing for periodicity: a model-independent approach to flux crosstalk calibration for superconducting circuits Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-02-02 X Dai, R Trappen, R Yang, S M Disseler, J I Basham, J Gibson, A J Melville, B M Niedzielski, R Das, D K Kim, J L Yoder, S J Weber, C F Hirjibehedin, D A Lidar, A Lupascu
Flux tunability is an important engineering resource for superconducting circuits. Large-scale quantum computers based on flux-tunable superconducting circuits face the problem of flux crosstalk, which needs to be accurately calibrated to realize high-fidelity quantum operations. Typical calibration methods either assume that circuit elements can be effectively decoupled and simple models can be applied
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Wafer-scale uniformity of Dolan-bridge and bridgeless Manhattan-style Josephson junctions for superconducting quantum processors Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-02-02 Nandini Muthusubramanian, Matvey Finkel, Pim Duivestein, Christos Zachariadis, Sean L M van der Meer, Hendrik M Veen, Marc W Beekman, Thijs Stavenga, Alessandro Bruno, Leonardo DiCarlo
We investigate die-level and wafer-scale uniformity of Dolan-bridge and bridgeless Manhattan-style Josephson junctions, using multiple substrates with and without through-silicon vias (TSVs). Dolan junctions fabricated on planar substrates have the highest yield and lowest room-temperature conductance spread, equivalent to ∼100MHz in transmon frequency. In TSV-integrated substrates, Dolan junctions
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Efficient quantum simulation of nonlinear interactions using SNAP and Rabi gates Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-01-30 Kimin Park, Petr Marek, Radim Filip
Quantum simulations provide means to probe challenging problems within controllable quantum systems. However, implementing or simulating deep-strong nonlinear couplings between bosonic oscillators on physical platforms remains a challenge. We present a deterministic simulation technique that efficiently and accurately models nonlinear bosonic dynamics. This technique alternates between tunable Rabi
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Computing electronic correlation energies using linear depth quantum circuits Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-01-29 Chong Hian Chee, Adrian M Mak, Daniel Leykam, Panagiotis Kl Barkoutsos, Dimitris G Angelakis
Efficient computation of molecular energies is an exciting application of quantum computing for quantum chemistry, but current noisy intermediate-scale quantum (NISQ) devices can only execute shallow circuits, limiting existing variational quantum algorithms, which require deep entangling quantum circuit ansatzes to capture correlations, to small molecules. Here we demonstrate a variational NISQ-friendly
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Generation and characterization of polarization-entangled states using quantum dot single-photon sources Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-01-22 Mauro Valeri, Paolo Barigelli, Beatrice Polacchi, Giovanni Rodari, Gianluca De Santis, Taira Giordani, Gonzalo Carvacho, Nicolò Spagnolo, Fabio Sciarrino
Single-photon sources based on semiconductor quantum dots find several applications in quantum information processing due to their high single-photon indistinguishability, on-demand generation, and low multiphoton emission. In this context, the generation of entangled photons represents a challenging task with a possible solution relying on the interference in probabilistic gates of identical photons
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Experimentally ruling out joint reality based on operational completeness Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-01-19 Qiuxin Zhang, Yu Xiang, Xiaoting Gao, Chenhao Zhu, Yuxin Wang, Liangyu Ding, Xiang Zhang, Shuaining Zhang, Shuming Cheng, Michael J W Hall, Qiongyi He, Wei Zhang
Whether the observables of a physical system admit real values is of fundamental importance to a deep understanding of nature. In this work, we report a device-independent experiment to confirm that the joint reality of two observables on a single two-level system is incompatible with the assumption of operational completeness, which is strictly weaker than that of preparation noncontextuality. We
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Comment on ‘From counterportation to local wormholes’ Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-01-04 Justin Dressel, Gregory Reznik, Lev Vaidman
Hatim Salih discovered a method for transferring a quantum state with no particles present in the transmission channel, which he named counterportation. Recently (Salih 2023 Quantum Sci. Technol. 8 025016), he presented a feasible procedure for its implementation. The modification of the protocol by Aharonov and Vaidman, adopted by Salih, justifies the claim that no photons were present in the transmission
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Indistinguishability-assisted two-qubit entanglement distillation Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-01-04 Farzam Nosrati, Bruno Bellomo, Gabriele De Chiara, Giuseppe Compagno, Roberto Morandotti, Rosario Lo Franco
Production of quantum states exhibiting a high degree of entanglement out of noisy conditions is one of the main goals of quantum information science. Here, we provide a conditional yet efficient entanglement distillation method which functions within the framework of spatially localized operations and classical communication. This method exploits indistinguishability effects due to the spatial overlap
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Quantum circuits for measuring weak values, Kirkwood–Dirac quasiprobability distributions, and state spectra Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-01-04 Rafael Wagner, Zohar Schwartzman-Nowik, Ismael L Paiva, Amit Te’eni, Antonio Ruiz-Molero, Rui Soares Barbosa, Eliahu Cohen, Ernesto F Galvão
Weak values and Kirkwood–Dirac (KD) quasiprobability distributions have been independently associated with both foundational issues in quantum theory and advantages in quantum metrology. We propose simple quantum circuits to measure weak values, KD distributions, and spectra of density matrices without the need for post-selection. This is achieved by measuring unitary-invariant, relational properties
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Building spatial symmetries into parameterized quantum circuits for faster training Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-01-04 Frédéric Sauvage, Martín Larocca, Patrick J Coles, M Cerezo
Practical success of quantum learning models hinges on having a suitable structure for the parameterized quantum circuit. Such structure is defined both by the types of gates employed and by the correlations of their parameters. While much research has been devoted to devising adequate gate-sets, typically respecting some symmetries of the problem, very little is known about how their parameters should
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Amplitude amplification-inspired QAOA: improving the success probability for solving 3SAT Quantum Sci. Technol. (IF 6.7) Pub Date : 2024-01-04 Alexander Mandl, Johanna Barzen, Marvin Bechtold, Frank Leymann, Karoline Wild
The Boolean satisfiability problem (SAT), in particular 3SAT with its bounded clause size, is a well-studied problem since a wide range of decision problems can be reduced to it. The Quantum Approximate Optimization Algorithm (QAOA) is a promising candidate for solving 3SAT for Noisy Intermediate-Scale Quantum devices in the near future due to its simple quantum ansatz. However, although QAOA generally
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Extending the variational quantum eigensolver to finite temperatures Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-12-22 Johannes Selisko, Maximilian Amsler, Thomas Hammerschmidt, Ralf Drautz, Thomas Eckl
We present a variational quantum thermalizer (VQT), called quantum-VQT (qVQT), which extends the variational quantum eigensolver to finite temperatures. The qVQT makes use of an intermediate measurement between two variational circuits to encode a density matrix on a quantum device. A classical optimization provides the thermal state and, simultaneously, all associated excited states of a quantum mechanical
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Security of quantum key distribution with imperfect phase randomisation Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-12-22 Guillermo Currás-Lorenzo, Shlok Nahar, Norbert Lütkenhaus, Kiyoshi Tamaki, Marcos Curty
The performance of quantum key distribution (QKD) is severely limited by multiphoton emissions, due to the photon-number-splitting attack. The most efficient solution, the decoy-state method, requires that the phases of all transmitted pulses are independent and uniformly random. In practice, however, these phases are often correlated, especially in high-speed systems, which opens a security loophole
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On readout and initialisation fidelity by finite demolition single shot readout Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-12-19 Majid Zahedian, Max Keller, Minsik Kwon, Javid Javadzade, Jonas Meinel, Vadim Vorobyov, Jörg Wrachtrup
Ideal projective quantum measurement makes the system state collapse in one of the observable operator eigenstates |ϕα⟩ , making it a powerful tool for preparing the system in the desired pure state. Nevertheless, experimental realisations of projective measurement are not ideal. During the measurement time needed to overcome the classical noise of the apparatus, the system state is often (slightly)
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Quantum optical induced-coherence tomography by a hybrid interferometer Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-12-19 Eun Mi Kim, Sun Kyung Lee, Sang Min Lee, Myeong Soo Kang, Hee Su Park
Quantum interferometry based on induced-coherence phenomena has demonstrated the possibility of undetected-photon measurements. Perturbation in the optical path of probe photons can be detected by interference signals generated by quantum mechanically correlated twin photons propagating through a different path, possibly at a different wavelength. To the best of our knowledge, this work demonstrates
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Quantum-classical hybrid neural networks in the neural tangent kernel regime Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-12-18 Kouhei Nakaji, Hiroyuki Tezuka, Naoki Yamamoto
Recently, quantum neural networks or quantum–classical neural networks (qcNN) have been actively studied, as a possible alternative to the conventional classical neural network (cNN), but their practical and theoretically-guaranteed performance is still to be investigated. In contrast, cNNs and especially deep cNNs, have acquired several solid theoretical basis; one of those basis is the neural tangent
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Certification of non-Gaussian Einstein–Podolsky–Rosen steering Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-12-14 Mingsheng Tian, Zihang Zou, Da Zhang, David Barral, Kamel Bencheikh, Qiongyi He, Feng-Xiao Sun, Yu Xiang
Non-Gaussian quantum states are a known necessary resource for reaching a quantum advantage and for violating Bell inequalities in continuous variable systems. As one kind of manifestation of quantum correlations, Einstein–Podolsky–Rosen steering enables verification of shared entanglement even when one of the subsystems is not characterized. However, how to detect and classify such an effect for non-Gaussian
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Large-alphabet time-bin quantum key distribution and Einstein–Podolsky–Rosen steering via dispersive optics Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-12-01 Kai-Chi Chang, Murat Can Sarihan, Xiang Cheng, Zheshen Zhang, Chee Wei Wong
Quantum key distribution (QKD) has established itself as a groundbreaking technology, showcasing inherent security features that are fundamentally proven. Qubit-based QKD protocols that rely on binary encoding encounter an inherent constraint related to the secret key capacity. This limitation restricts the maximum secret key capacity to one bit per photon. On the other hand, qudit-based QKD protocols
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Clock synchronization with pulsed single photon sources Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-12-01 Christopher Spiess, Fabian Steinlechner
Photonic quantum technology requires precise, time-resolved identification of photodetection events. In distributed quantum networks with spatially separated and drifting time references, achieving high precision is particularly challenging. Here we build on recent advances of using single-photons for time transfer and employ and quantify a fast postprocessing scheme designed to pulsed single-photon
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Variational quantum state discriminator for supervised machine learning Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-11-21 Dongkeun Lee, Kyunghyun Baek, Joonsuk Huh, Daniel K Park
Quantum state discrimination (QSD) is a fundamental task in quantum information processing with numerous applications. We present a variational quantum algorithm that performs the minimum-error QSD, called the variational quantum state discriminator (VQSD). The VQSD uses a parameterized quantum circuit that is trained by minimizing a cost function derived from the QSD, and finds the optimal positive-operator
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Quantum logical controlled-NOT gate in a lithium niobate-on-insulator photonic quantum walk Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-11-17 Robert J Chapman, Samuel Häusler, Giovanni Finco, Fabian Kaufmann, Rachel Grange
The two-qubit controlled-NOT gate is one of the central entangling operations in quantum information technology. The controlled-NOT gate for single photon qubits is normally realized as a network of five individual beamsplitters on six optical modes. Quantum walks (QWs) are an alternative photonic architecture involving arrays of coupled waveguides, which have been successful for investigating condensed
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Verification of continuous-variable quantum memories Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-11-15 Paolo Abiuso
A proper quantum memory is argued to consist in a quantum channel which cannot be simulated with a measurement followed by classical information storage and a final state preparation, i.e. with an entanglement breaking (EB) channel. The verification of quantum memories (non-EB channels) is a task in which an honest user wants to test the quantum memory of an untrusted, remote provider. This task is
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A fault-tolerant variational quantum algorithm with limited T-depth Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-11-13 Hasan Sayginel, Francois Jamet, Abhishek Agarwal, Dan E Browne, Ivan Rungger
We propose a variational quantum eigensolver (VQE) algorithm that uses a fault-tolerant (FT) gate-set, and is hence suitable for implementation on a future error-corrected quantum computer. VQE quantum circuits are typically designed for near-term, noisy quantum devices and have continuously parameterized rotation gates as the central building block. On the other hand, an FT quantum computer (FTQC)
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Time optimal quantum state transfer in a fully-connected quantum computer Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-11-10 Casey Jameson, Bora Basyildiz, Daniel Moore, Kyle Clark, Zhexuan Gong
The speed limit of quantum state transfer (QST) in a system of interacting particles is not only important for quantum information processing, but also directly linked to Lieb–Robinson-type bounds that are crucial for understanding various aspects of quantum many-body physics. For strongly long-range interacting systems such as a fully-connected quantum computer, such a speed limit is still unknown
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Quadrupole transitions and quantum gates protected by continuous dynamic decoupling Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-11-10 V J Martínez-Lahuerta, L Pelzer, K Dietze, L Krinner, P O Schmidt, K Hammerer
Dynamical decoupling techniques are a versatile tool for engineering quantum states with tailored properties. In trapped ions, nested layers of continuous dynamical decoupling (CDD) by means of radio-frequency field dressing can cancel dominant magnetic and electric shifts and therefore provide highly prolonged coherence times of electronic states. Exploiting this enhancement for frequency metrology
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Decomposition of matrix product states into shallow quantum circuits Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-11-08 Manuel S Rudolph, Jing Chen, Jacob Miller, Atithi Acharya, Alejandro Perdomo-Ortiz
Tensor networks (TNs) are a family of computational methods built on graph-structured factorizations of large tensors, which have long represented state-of-the-art methods for the approximate simulation of complex quantum systems on classical computers. The rapid pace of recent advancements in numerical computation, notably the rise of GPU and TPU hardware accelerators, have allowed TN algorithms to
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T-depth-optimized quantum search with quantum data-access machine Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-11-01 Jung Jun Park, Kyunghyun Baek, M S Kim, Hyunchul Nha, Jaewan Kim, Jeongho Bang
Quantum search algorithms offer a remarkable advantage of quadratic reduction in query complexity using quantum superposition principle. However, how an actual architecture may access and handle the database in a quantum superposed state has been largely unexplored so far; the quantum state of data was simply assumed to be prepared and accessed by a black-box operation—so-called oracle, even though
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Pauli transfer matrix direct reconstruction: channel characterization without full process tomography Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-10-31 Simone Roncallo, Lorenzo Maccone, Chiara Macchiavello
We present a tomographic protocol for the characterization of multiqubit quantum channels. We discuss a specific class of input states, for which the set of Pauli measurements at the output of the channel directly relates to its Pauli transfer matrix components. We compare our results to those of standard quantum process tomography, showing an exponential reduction in the number of different experimental
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Precise image generation on current noisy quantum computing devices Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-10-30 Florian Rehm, Sofia Vallecorsa, Kerstin Borras, Dirk Krücker, Michele Grossi, Valle Varo
The quantum angle generator (QAG) is a new full quantum machine learning model designed to generate accurate images on current noise intermediate scale quantum devices. Variational quantum circuits form the core of the QAG model, and various circuit architectures are evaluated. In combination with the so-called MERA-upsampling architecture, the QAG model achieves excellent results, which are analyzed
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Boundary-induced singularity in strongly-correlated quantum systems at finite temperature Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-10-26 Ding-Zu Wang, Guo-Feng Zhang, Maciej Lewenstein, Shi-Ju Ran
Exploring the bulk-boundary correspondences and the boundary-induced phenomena in the strongly-correlated quantum systems belongs to the most fundamental topics of condensed matter physics. In this work, we study the bulk-boundary competition in a simulative Hamiltonian, with which the thermodynamic properties of the infinite-size translationally-invariant system can be optimally mimicked. The simulative
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Cryogenic ion trap system for high-fidelity near-field microwave-driven quantum logic Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-10-25 M A Weber, C Löschnauer, J Wolf, M F Gely, R K Hanley, J F Goodwin, C J Ballance, T P Harty, D M Lucas
We report the design, fabrication, and characterization of a cryogenic ion trap system for the implementation of quantum logic driven by near-field microwaves. The trap incorporates an on-chip microwave resonator with an electrode geometry designed to null the microwave field component that couples directly to the qubit, while giving a large field gradient for driving entangling logic gates. We map
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Production of Fock mixtures in trapped ions for motional metrology Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-10-23 Antonis Delakouras, Daniel Rodríguez, Javier Cerrillo
We present a protocol to produce a class of non-thermal Fock state mixtures in trapped ions. This class of states features a clear metrological advantage with respect to the ground state, thus overcoming the standard quantum limit without the need for full sideband cooling and Fock-state preparation on a narrow electronic transition. The protocol consists in the cyclic repetition of red-sideband (RSB)
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Physical entanglement between localized orbitals Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-10-16 Lexin Ding, Gesa Dünnweber, Christian Schilling
The goal of the present work is to guide the development of quantum technologies in the context of fermionic systems. For this, we first elucidate the process of entanglement swapping in electron systems such as atoms, molecules or solid bodies. This demonstrates the significance of the number-parity superselection rule and highlights the relevance of localized few-orbital subsystems for quantum information
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Modularized and scalable compilation for double quantum dot quantum computing Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-10-13 Run-Hong He, Xu-Sheng Xu, Mark S Byrd, Zhao-Ming Wang
Any quantum program on a realistic quantum device must be compiled into an executable form while taking into account the underlying hardware constraints. Stringent restrictions on architecture and control imposed by physical platforms make this very challenging. In this paper, based on the quantum variational algorithm, we propose a novel scheme to train an Ansatz circuit and realize high-fidelity
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High-dimensional quantum key distribution using energy-time entanglement over 242 km partially deployed fiber Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-10-12 Jingyuan Liu, Zhihao Lin, Dongning Liu, Xue Feng, Fang Liu, Kaiyu Cui, Yidong Huang, Wei Zhang
Entanglement-based quantum key distribution (QKD) is an essential ingredient in quantum communication, owing to the property of source-independent security and the potential on constructing large-scale quantum communication networks. However, implementation of entanglement-based QKD over long-distance optical fiber links is still challenging, especially over deployed fibers. In this work, we report
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Linear-depth quantum circuits for loading Fourier approximations of arbitrary functions Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-10-11 Mudassir Moosa, Thomas W Watts, Yiyou Chen, Abhijat Sarma, Peter L McMahon
The ability to efficiently load functions on quantum computers with high fidelity is essential for many quantum algorithms, including those for solving partial differential equations and Monte Carlo estimation. In this work, we introduce the Fourier series loader (FSL) method for preparing quantum states that exactly encode multi-dimensional Fourier series using linear-depth quantum circuits. Specifically
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Boosting quantum amplitude exponentially in variational quantum algorithms Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-10-10 Thi Ha Kyaw, Micheline B Soley, Brandon Allen, Paul Bergold, Chong Sun, Victor S Batista, Alán Aspuru-Guzik
We introduce a family of variational quantum algorithms, which we coin as quantum iterative power algorithms (QIPAs), and demonstrate their capabilities as applied to global-optimization numerical experiments. Specifically, we demonstrate the QIPA based on a double exponential oracle as applied to ground state optimization of the H 2 molecule, search for the transmon qubit ground-state, and biprime
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Quantum kernel evaluation via Hong–Ou–Mandel interference Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-10-09 C Bowie, S Shrapnel, M J Kewming
One of the fastest growing areas of interest in quantum computing is its use within machine learning methods, in particular through the application of quantum kernels. Despite this large interest, there exist very few proposals for relevant physical platforms to evaluate quantum kernels. In this article, we propose and simulate a protocol capable of evaluating quantum kernels using Hong–Ou–Mandel interference
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Diabatic quantum annealing for the frustrated ring model Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-10-06 Jeremy Côté, Frédéric Sauvage, Martín Larocca, Matías Jonsson, Lukasz Cincio, Tameem Albash
Quantum annealing (QA) is a continuous-time heuristic quantum algorithm for solving or approximately solving classical optimization problems. The algorithm uses a schedule to interpolate between a driver Hamiltonian with an easy-to-prepare ground state and a problem Hamiltonian whose ground state encodes solutions to an optimization problem. The standard implementation relies on the evolution being
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Federated quanvolutional neural network: a new paradigm for collaborative quantum learning Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-10-05 Amandeep Singh Bhatia, Sabre Kais, Muhammad Ashraful Alam
In recent years, the concept of federated machine learning has been actively driven by scientists to ease the privacy concerns of data owners. Currently, the combination of machine learning and quantum computing technologies is a hot industry topic and is positioned to be a major disruptor. It has become an effective new tool for reshaping several industries ranging from healthcare to finance. Data
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Efficient parallelization of quantum basis state shift Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-09-28 Lj Budinski, O Niemimäki, R Zamora-Zamora, V Lahtinen
Basis state shift is central to many quantum algorithms, most notably the quantum walk. Efficient implementations are of major importance for achieving a quantum speedup for computational applications. We optimize the state shift algorithm by incorporating the shift in different directions in parallel. This provides a significant reduction in the depth of the quantum circuit in comparison to the currently
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Orbital expansion variational quantum eigensolver Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-09-27 Yusen Wu, Zigeng Huang, Jinzhao Sun, Xiao Yuan, Jingbo B Wang, Dingshun Lv
Variational quantum eigensolver (VQE) has emerged as a promising method for investigating ground state properties in quantum chemistry, materials science, and condensed matter physics. However, the conventional VQE method generally lacks systematic improvement and convergence guarantees, particularly when dealing with strongly correlated systems. In light of these challenges, we present a novel framework
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Optimal, hardware native decomposition of parameterized multi-qubit Pauli gates Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-09-25 P V Sriluckshmy, Vicente Pina-Canelles, Mario Ponce, Manuel G Algaba, Fedor Šimkovic IV, Martin Leib
We show how to efficiently decompose a parameterized multi-qubit Pauli (PMQP) gate into native parameterized two-qubit Pauli (P2QP) gates minimizing both the circuit depth and the number of P2QP gates. Given a realistic quantum computational model, we argue that the technique is optimal in terms of the number of hardware native gates and the overall depth of the decomposition. Starting from PMQP gate
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Graphical structures for design and verification of quantum error correction Quantum Sci. Technol. (IF 6.7) Pub Date : 2023-09-22 Nicholas Chancellor, Aleks Kissinger, Stefan Zohren, Joschka Roffe, Dominic Horsman
We introduce a high-level graphical framework for designing and analysing quantum error correcting codes, centred on what we term the coherent parity check (CPC). The graphical formulation is based on the diagrammatic tools of the ZX-calculus of quantum observables. The resulting framework leads to a construction for stabilizer codes that allows us to design and verify a broad range of quantum codes