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  • An updated LLVM-based quantum research compiler with further OpenQASM support
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-05-27
    Andrew Litteken, Yung-Ching Fan, Devina Singh, Margaret Martonosi and Frederic T Chong

    Quantum computing is a rapidly growing field with the potential to change how we solve previously intractable problems. Emerging hardware is approaching a complexity that requires increasingly sophisticated programming and control. Scaffold is an older quantum programming language that was originally designed for resource estimation for far-future, large quantum machines, and ScaffCC is the corresponding

  • QuESTlink—Mathematica embiggened by a hardware-optimised quantum emulator
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-05-27
    Tyson Jones and Simon Benjamin

    We introduce QuESTlink,pronounced ‘quest link’, an open-source Mathematicapackage which efficiently emulates quantum computers. By integratingwith the Quantum Exact Simulation Toolkit (QuEST), QuESTlink offers ahigh-level, expressive and usable interface to a high-performance, hardware-accelerated emulator. Requiring no installation, QuESTlink streamlines the powerful analysis capabilities of Mathematica

  • Quantum scrambling and the growth of mutual information
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-05-25
    Akram Touil and Sebastian Deffner

    Quantum information scrambling refers to the loss of local recoverability of quantum information, which has found widespread attention from high energy physics to quantum computing. In the present analysis we propose a possible starting point for the development of a comprehensive framework for the thermodynamics of scrambling. To this end, we prove that the growth of entanglement as quantified by

  • Applications of near-term photonic quantum computers: software and algorithms
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-05-20
    Thomas R Bromley, Juan Miguel Arrazola, Soran Jahangiri, Josh Izaac, Nicolás Quesada, Alain Delgado Gran, Maria Schuld, Jeremy Swinarton, Zeid Zabaneh and Nathan Killoran

    Gaussian boson sampling (GBS) is a near-term platform for photonic quantum computing. Recent efforts have led to the discovery of GBS algorithms with applications to graph-based problems, point processes, and molecular vibronic spectra in chemistry. The development of dedicated quantum software is a key enabler in permitting users to program devices and implement algorithms. In this work, we introduce

  • Figures of merit for quantum transducers
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-05-18
    Emil Zeuthen, Albert Schliesser, Anders S Sørensen and Jacob M Taylor

    Recent technical advances have sparked renewed interest in physical systems that couple simultaneously to different parts of the electromagnetic spectrum, thus enabling transduction of signals between vastly different frequencies at the level of single quanta. Such hybrid systems have demonstrated frequency conversion of classical signals and have the potential of enabling quantum state transfer, e

  • Training the quantum approximate optimization algorithm without access to a quantum processing unit
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-05-11
    Michael Streif and Martin Leib

    In this paper, we eliminate the classical outer learning loop of the quantum approximate optimization algorithm (QAOA) and present a strategy to find good parameters for QAOA based on topological arguments of the problem graph and tensor network techniques. Starting from the observation of the concentration of control parameters of QAOA, we find a way to classically infer parameters which scales polynomially

  • A quantum algorithm to efficiently sample from interfering binary trees
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-05-10
    Davide Provasoli, Benjamin Nachman, Christian Bauer and Wibe A de Jong

    Quantum computers provide an opportunity to efficiently sample from probability distributions that include non-trivial interference effects between amplitudes. Using a simple process wherein all possible state histories can be specified by a binary tree, we construct an explicit quantum algorithm for an important three-dimensional subspace of the parameter space that runs in polynomial time to sample

  • Quantum electronics and optics at the interface of solid neon and superfluid helium
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-05-10
    Dafei Jin

    We predict a new quantum electronic structure at the interface between two condensed phases of noble-gas elements: solid neon and superfluid helium. An excess electron injected onto this interface self-confines its wavefunction into a nanometric dome structure. Its size varies with pressure and optical transitions cover a broad mid-infrared spectrum. A collection of such electrons can form a classical

  • Intel Quantum Simulator: a cloud-ready high-performance simulator of quantum circuits
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-05-10
    Gian Giacomo Guerreschi, Justin Hogaboam, Fabio Baruffa and Nicolas P D Sawaya

    Classical simulation of quantum computers will continue to play an essential role in the progress of quantum information science, both for numerical studies of quantum algorithms and for modeling noise and errors. Here we introduce the latest release of Intel Quantum Simulator (IQS), formerly known as qHiPSTER. The high-performance computing (HPC) capability of the software allows users to leverage

  • Engineering electro-optics in SiGe/Si waveguides for quantum transduction
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-05-06
    Jason Orcutt, Hanhee Paik, Lev Bishop, Chi Xiong, Ryan Schilling and Abram Falk

    High efficiency microwave-optical transduction for quantum-state transfer remains an outstanding technical challenge. Resonant electro-optic transduction via three-wave mixing is an attractive solution, with a simple operating principle that does not rely on intermediate quantum states. However, the intrinsic optical and microwave losses of electro-optic materials with large Pockels coefficients have

  • Resonant exchange operation in triple-quantum-dot qubits for spin–photon transduction
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-05-06
    Andrew Pan, Tyler E Keating, Mark F Gyure, Emily J Pritchett, Samuel Quinn, Richard S Ross, Thaddeus D Ladd and Joseph Kerckhoff

    Triple quantum dots (TQDs) are promising semiconductor spin qubits because of their all-electrical control via fast, tunable exchange interactions and immunity to global magnetic fluctuations. These qubits can experience strong transverse interaction with photons in the resonant exchange (RX) regime, when exchange is simultaneously active on both qubit axes. However, most theoretical work has been

  • Randomized benchmarking in the analogue setting
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-04-29
    E Derbyshire, J Yago Malo, A J Daley, E Kashefi and P Wallden

    Current development in programmable analogue quantum simulators (AQS), whose physical implementation can be realised in the near-term compared to those of large-scale digital quantum computers, highlights the need for robust testing techniques in analogue platforms. Methods to properly certify or benchmark AQS should be efficiently scalable, and also provide a way to deal with errors from state preparation

  • A silicon‐organic hybrid platform for quantum microwave-to-optical transduction
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-04-29
    Jeremy D Witmer, Timothy P McKenna, Patricio Arrangoiz-Arriola, Raphaël Van Laer, E Alex Wollack, Francis Lin, Alex K-Y Jen, Jingdong Luo and Amir H Safavi-Naeini

    Low-loss fiber optic links have the potential to connect superconducting quantum processors together over long distances to form large scale quantum networks. A key component of these future networks is a quantum transducer that coherently and bidirectionally converts photons from microwave frequencies to optical frequencies. We present a platform for electro-optic photon conversion based on silicon‐organic

  • Inter-qubit interaction mediated by collective modes in a linear array of three-dimensional cavities
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-04-27
    Dmytro Dubyna and Watson Kuo

    A design of LEGO-like construction set that allows assembling of different linear arrays of three-dimensional (3D) cavities and qubits for circuit quantum electrodynamics experiments has been developed. A study of electromagnetic properties of qubit-3D cavity arrays has been done by using high frequency structure simulator (HFSS). A technique for estimation of inter-qubit coupling strength between

  • Quantum-classical simulation of two-site dynamical mean-field theory on noisy quantum hardware
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-04-27
    Trevor Keen, Thomas Maier, Steven Johnston and Pavel Lougovski

    We report on a quantum–classical simulation of the single-band Hubbard model using two-site dynamical mean-field theory (DMFT). Our approach uses IBM’s superconducting qubit chip to compute the zero-temperature impurity Green’s function in the time domain and a classical computer to fit the measured Green’s functions and extract their frequency domain parameters. We find that the quantum circuit synthesis

  • Logical performance of 9 qubit compass codes in ion traps with crosstalk errors
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-04-27
    Dripto M Debroy, Muyuan Li, Shilin Huang and Kenneth R Brown

    We simulate four quantum error correcting codes under error models inspired by realistic noise sources in near-term ion trap quantum computers: T 2 dephasing, gate overrotation, and crosstalk. We use this data to find preferred codes for given error parameters along with logical error biases and a pseudothreshold which compares the physical and logical gate failure rates for a CNOT gate. Using these

  • Establishing the quantum supremacy frontier with a 281 Pflop/s simulation
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-04-27
    Benjamin Villalonga, Dmitry Lyakh, Sergio Boixo, Hartmut Neven, Travis S Humble, Rupak Biswas, Eleanor G Rieffel, Alan Ho and Salvatore Mandrà

    Noisy intermediate-scale quantum (NISQ) computers are entering an era in which they can perform computational tasks beyond the capabilities of the most powerful classical computers, thereby achieving ‘quantum supremacy’, a major milestone in quantum computing. NISQ supremacy requires comparison with a state-of-the-art classical simulator. We report HPC simulations of hard random quantum circuits (RQC)

  • A quantum-classical cloud platform optimized for variational hybrid algorithms
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-04-20
    Peter J Karalekas, Nikolas A Tezak, Eric C Peterson, Colm A Ryan, Marcus P da Silva and Robert S Smith

    In order to support near-term applications of quantum computing, a new compute paradigm has emerged—the quantum-classical cloud—in which quantum computers (QPUs) work in tandem with classical computers (CPUs) via a shared cloud infrastructure. In this work, we enumerate the architectural requirements of a quantum-classical cloud platform, and present a framework for benchmarking its runtime performance

  • MCTDH-X : The multiconfigurational time-dependent Hartree method for indistinguishable particles software
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-04-20
    Rui Lin, Paolo Molignini, Luca Papariello, Marios C Tsatsos, Camille Lévêque, Storm E Weiner, Elke Fasshauer, R Chitra and Axel U J Lode

    We introduce and describe the multiconfigurational time-depenent Hartree for indistinguishable particles (MCTDH-X) software, which is hosted, documented, and distributedat http://ultracold.org [http://ultracold.org] . This powerful tool allows the investigation of ground state properties and dynamics of interacting quantum many-body systems in different spatial dimensions. The MCTDH-X software is a

  • Quantum circuit optimizations for NISQ architectures
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-03-30
    Beatrice Nash, Vlad Gheorghiu and Michele Mosca

    Currently available quantum computing hardware platforms have limited 2-qubit connectivity among their addressable qubits. In order to run a generic quantum algorithm on such a platform, one has to transform the initial logical quantum circuit describing the algorithm into an equivalent one that obeys the connectivity restrictions. In this work we construct a circuit synthesis scheme that takes as

  • Impact of qubit connectivity on quantum algorithm performance
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-03-30
    Adam Holmes, Sonika Johri, Gian Giacomo Guerreschi, James S Clarke and A Y Matsuura

    Quantum computing hardware is undergoing rapid development from proof-of-principle devices to scalable machines that could eventually challenge classical supercomputers on specific tasks. On platforms with local connectivity, the transition from one- to two-dimensional arrays of qubits is seen as a natural technological step to increase the density of computing power and to reduce the routing cost

  • Anomalous values, Fisher information, and contextuality, in generalized quantum measurements
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-03-17
    Valeria Cimini, Ilaria Gianani, Fabrizio Piacentini, Ivo Pietro Degiovanni and Marco Barbieri

    Postselection following weak measurements has long been investigated for its peculiar manifestation of quantum signatures. In particular, the postselected events can give rise to anomalous values lying outside the spectrum of the measured quantity, and may provide enhanced Fisher information. Furthermore, the Pusey inequality highlights that, for extremely weak measurements, non-contextual models cannot

  • Long-lived state in a four-spin system hyperpolarized at room temperature
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-03-17
    Koichiro Miyanishi, Naoki Ichijo, Makoto Motoyama, Akinori Kagawa, Makoto Negoro and Masahiro Kitagawa

    A solution with hyperpolarized nuclear spins encoded into a long-lived state has been utilized for sensing chemical phenomena. In a conventional way, nuclear spins are hyperpolarized at very low temperatures. In this work, we demonstrate the encoding of a four-nuclear-spin system hyperpolarized at room temperature into a long-lived state in a solution. We apply the solution with the long-lived state

  • Saturating the quantum Cramér–Rao bound using LOCC
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-03-17
    Sisi Zhou, Chang-Ling Zou and Liang Jiang

    The quantum Cramér–Rao bound (QCRB) provides an ultimate precision limit allowed by quantum mechanics in parameter estimation. Given any quantum state dependent on a single parameter, there is always a positive-operator valued measurement (POVM) saturating the QCRB. However, the QCRB-saturating POVM cannot always be implemented efficiently, especially in multipartite systems. In this paper, we show

  • Levitated cavity optomechanics in high vacuum
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-03-17
    Uroš Delić, David Grass, Manuel Reisenbauer, Tobias Damm, Martin Weitz, Nikolai Kiesel and Markus Aspelmeyer

    We report dispersive coupling of an optically trapped nanoparticle to the field of a Fabry–Perot cavity in high vacuum. We demonstrate nanometer-level control in positioning the particle with respect to the cavity field, which allows access to linear, quadratic, and tertiary optomechanical interactions in the resolved sideband regime. We determine all relevant coupling rates of the system, i.e. mechanical

  • Perspectives on quantum transduction
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-03-17
    Nikolai Lauk, Neil Sinclair, Shabir Barzanjeh, Jacob P Covey, Mark Saffman, Maria Spiropulu and Christoph Simon

    Quantum transduction, the process of converting quantum signals from one form of energy to another, is an important area of quantum science and technology. The present perspective article reviews quantum transduction between microwave and optical photons, an area that has recently seen a lot of activity and progress because of its relevance for connecting superconducting quantum processors over long

  • Multimode Fock states with large photon number: effective descriptions and applications in quantum metrology
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-02-18
    M Perarnau-Llobet, A González-Tudela and J I Cirac

    We develop general tools to characterise and efficiently compute relevant observables of multimode N -photon states generated in nonlinear decays in one-dimensional waveguides. We then consider optical interferometry in a Mach–Zender interferometer where a d -mode photonic state enters in each arm of the interferometer. We derive a simple expression for the quantum Fisher information in terms of the

  • XACC: a system-level software infrastructure for heterogeneous quantum–classical computing
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-02-04
    Alexander J McCaskey, Dmitry I Lyakh, Eugene F Dumitrescu, Sarah S Powers and Travis S Humble

    Quantum programming techniques and software have advanced significantly over the past five years, with a majority focusing on high-level language frameworks targeting remote REST library APIs. As quantum computing architectures advance and become more widely available, lower-level, system software infrastructures will be needed to enable tighter, co-processor programming and access models. Here we

  • Generation of hybrid maximally entangled states in a one-dimensional quantum walk
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-02-04
    Aikaterini Gratsea, Maciej Lewenstein and Alexandre Dauphin

    We study the generation of hybrid entanglement in a one-dimensional quantum walk. In particular, we explore the preparation of maximally entangled states between position and spin degrees of freedom. We address it as an optimization problem, where the cost function is the Schmidt norm. We then benchmark the algorithm and compare the generation of entanglement between the Hadamard quantum walk, the

  • Machine learning design of a trapped-ion quantum spin simulator
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-01-16
    Yi Hong Teoh, Marina Drygala, Roger G Melko and Rajibul Islam

    Trapped ions have emerged as one of the highest quality platforms for the quantum simulation of interacting spin models of interest to various fields of physics. In such simulators, two effective spins can be made to interact with arbitrary strengths by coupling to the collective vibrational or phonon states of ions, controlled by precisely tuned laser beams. However, the task of determining laser

  • Modeling and control of a reconfigurable photonic circuit using deep learning
    Quantum Sci. Technol. (IF 3.022) Pub Date : 2020-01-16
    Akram Youssry, Robert J Chapman, Alberto Peruzzo, Christopher Ferrie and Marco Tomamichel

    The complexity of experimental quantum information processing devices is increasing rapidly, requiring new approaches to control them. In this paper, we address the problems of practically modeling and controlling an integrated optical waveguide array chip—a technology expected to have many applications in telecommunications and optical quantum information processing. This photonic circuit can be electrically

  • High coherence plane breaking packaging for superconducting qubits.
    Quantum Sci. Technol. Pub Date : 2018-05-05
    Nicholas T Bronn,Vivekananda P Adiga,Salvatore B Olivadese,Xian Wu,Jerry M Chow,David P Pappas

    We demonstrate a pogo pin package for a superconducting quantum processor specifically designed with a nontrivial layout topology (e.g., a center qubit that cannot be accessed from the sides of the chip). Two experiments on two nominally identical superconducting quantum processors in pogo packages, which use commercially available parts and require modest machining tolerances, are performed at low

  • Rigidity of the magic pentagram game.
    Quantum Sci. Technol. Pub Date : 2018-02-13
    Amir Kalev,Carl A Miller

    A game is rigid if a near-optimal score guarantees, under the sole assumption of the validity of quantum mechanics, that the players are using an approximately unique quantum strategy. Rigidity has a vital role in quantum cryptography as it permits a strictly classical user to trust behavior in the quantum realm. This property can be traced back as far as 1998 (Mayers and Yao) and has been proved for

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