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Mitiq: A software package for error mitigation on noisy quantum computers Quantum (IF 6.439) Pub Date : 2022-08-11 Ryan LaRose, Andrea Mari, Sarah Kaiser, Peter J. Karalekas, Andre A. Alves, Piotr Czarnik, Mohamed El Mandouh, Max H. Gordon, Yousef Hindy, Aaron Robertson, Purva Thakre, Misty Wahl, Danny Samuel, Rahul Mistri, Maxime Tremblay, Nick Gardner, Nathaniel T. Stemen, Nathan Shammah, William J. Zeng
We introduce Mitiq, a Python package for error mitigation on noisy quantum computers. Error mitigation techniques can reduce the impact of noise on near-term quantum computers with minimal overhead in quantum resources by relying on a mixture of quantum sampling and classical post-processing techniques. Mitiq is an extensible toolkit of different error mitigation methods, including zero-noise extrapolation
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Coherent information of a quantum channel or its complement is generically positive Quantum (IF 6.439) Pub Date : 2022-08-11 Satvik Singh, Nilanjana Datta
The task of determining whether a given quantum channel has positive capacity to transmit quantum information is a fundamental open problem in quantum information theory. In general, the coherent information needs to be computed for an unbounded number of copies of a channel in order to detect a positive value of its quantum capacity. However, in this paper, we show that the coherent information of
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Deviation bounds and concentration inequalities for quantum noises Quantum (IF 6.439) Pub Date : 2022-08-04 Tristan Benoist, Lisa Hänggli, Cambyse Rouzé
We provide a stochastic interpretation of non-commutative Dirichlet forms in the context of quantum filtering. For stochastic processes motivated by quantum optics experiments, we derive an optimal finite time deviation bound expressed in terms of the non-commutative Dirichlet form. Introducing and developing new non-commutative functional inequalities, we deduce concentration inequalities for these
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Fast Black-Box Quantum State Preparation Quantum (IF 6.439) Pub Date : 2022-08-04 Johannes Bausch
Quantum state preparation is an important ingredient for other higher-level quantum algorithms, such as Hamiltonian simulation, or for loading distributions into a quantum device to be used e.g. in the context of optimization tasks such as machine learning. Starting with a generic "black box" method devised by Grover in 2000, which employs amplitude amplification to load coefficients calculated by
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Security of quantum key distribution with detection-efficiency mismatch in the multiphoton case Quantum (IF 6.439) Pub Date : 2022-07-22 Anton Trushechkin
Detection-efficiency mismatch is a common problem in practical quantum key distribution (QKD) systems. Current security proofs of QKD with detection-efficiency mismatch rely either on the assumption of the single-photon light source on the sender side or on the assumption of the single-photon input of the receiver side. These assumptions impose restrictions on the class of possible eavesdropping strategies
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TFermion: A non-Clifford gate cost assessment library of quantum phase estimation algorithms for quantum chemistry Quantum (IF 6.439) Pub Date : 2022-07-20 Pablo A. M. Casares, Roberto Campos, M. A. Martin-Delgado
Quantum Phase Estimation is one of the most useful quantum computing algorithms for quantum chemistry and as such, significant effort has been devoted to designing efficient implementations. In this article, we introduce TFermion, a library designed to estimate the T-gate cost of such algorithms, for an arbitrary molecule. As examples of usage, we estimate the T-gate cost of a few simple molecules
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Measurement-based generation and preservation of cat and grid states within a continuous-variable cluster state Quantum (IF 6.439) Pub Date : 2022-07-20 Miller Eaton, Carlos González-Arciniegas, Rafael N. Alexander, Nicolas C. Menicucci, Olivier Pfister
We present an algorithm to reliably generate various quantum states critical to quantum error correction and universal continuous-variable (CV) quantum computing, such as Schrödinger cat states and Gottesman-Kitaev-Preskill (GKP) grid states, out of Gaussian CV cluster states. Our algorithm is based on the Photon-counting-Assisted Node-Teleportation Method (PhANTM), which uses standard Gaussian information
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Towards Quantum Advantage in Financial Market Risk using Quantum Gradient Algorithms Quantum (IF 6.439) Pub Date : 2022-07-20 Nikitas Stamatopoulos, Guglielmo Mazzola, Stefan Woerner, William J. Zeng
We introduce a quantum algorithm to compute the market risk of financial derivatives. Previous work has shown that quantum amplitude estimation can accelerate derivative pricing quadratically in the target error and we extend this to a quadratic error scaling advantage in market risk computation. We show that employing quantum gradient estimation algorithms can deliver a further quadratic advantage
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Finite Rate QLDPC-GKP Coding Scheme that Surpasses the CSS Hamming Bound Quantum (IF 6.439) Pub Date : 2022-07-20 Nithin Raveendran, Narayanan Rengaswamy, Filip Rozpędek, Ankur Raina, Liang Jiang, Bane Vasić
Quantum error correction has recently been shown to benefit greatly from specific physical encodings of the code qubits. In particular, several researchers have considered the individual code qubits being encoded with the continuous variable GottesmanKitaev-Preskill (GKP) code, and then imposed an outer discrete-variable code such as the surface code on these GKP qubits. Under such a concatenation
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Work and Fluctuations: Coherent vs. Incoherent Ergotropy Extraction Quantum (IF 6.439) Pub Date : 2022-07-14 Marcin Łobejko
We consider a quasi-probability distribution of work for an isolated quantum system coupled to the energy-storage device given by the ideal weight. Specifically, we analyze a trade-off between changes in average energy and changes in weight's variance, where work is extracted from the coherent and incoherent ergotropy of the system. Primarily, we reveal that the extraction of positive coherent ergotropy
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Finding out all locally indistinguishable sets of generalized Bell states Quantum (IF 6.439) Pub Date : 2022-07-14 Jiang-Tao Yuan, Ying-Hui Yang, Cai-Hong Wang
In general, for a bipartite quantum system $\mathbb{C}^{d}\otimes\mathbb{C}^{d}$ and an integer $k$ such that $4\leq k\le d$,there are few necessary and sufficient conditions for local discrimination of sets of $k$ generalized Bell states (GBSs) and it is difficult to locally distinguish $k$-GBS sets.The purpose of this paper is to completely solve the problem of local discrimination of GBS sets in
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Statistical time-domain characterization of non-periodic optical clocks Quantum (IF 6.439) Pub Date : 2022-07-14 Dario Cilluffo
Measuring time means counting the occurrence of periodic phenomena. Over the past centuries a major effort was put to make stable and precise oscillators to be used as clock regulators. Here we consider a different class of clocks based on stochastic clicking processes. We provide a rigorous statistical framework to study the performances of such devices and apply our results to a single coherently
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Naturally restricted subsets of nonsignaling correlations: typicality and convergence Quantum (IF 6.439) Pub Date : 2022-07-14 Pei-Sheng Lin, Tamás Vértesi, Yeong-Cherng Liang
It is well-known that in a Bell experiment, the observed correlation between measurement outcomes – as predicted by quantum theory – can be stronger than that allowed by local causality, yet not fully constrained by the principle of relativistic causality. In practice, the characterization of the set $Q$ of quantum correlations is carried out, often, through a converging hierarchy of outer approximations
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Quantum XYZ Product Codes Quantum (IF 6.439) Pub Date : 2022-07-14 Anthony Leverrier, Simon Apers, Christophe Vuillot
We study a three-fold variant of the hypergraph product code construction, differing from the standard homological product of three classical codes. When instantiated with 3 classical LDPC codes, this "XYZ product" yields a non CSS quantum LDPC code which might display a large minimum distance. The simplest instance of this construction, corresponding to the product of 3 repetition codes, is a non
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Computing Ground State Properties with Early Fault-Tolerant Quantum Computers Quantum (IF 6.439) Pub Date : 2022-07-11 Ruizhe Zhang, Guoming Wang, Peter Johnson
Significant effort in applied quantum computing has been devoted to the problem of ground state energy estimation for molecules and materials. Yet, for many applications of practical value, additional properties of the ground state must be estimated. These include Green's functions used to compute electron transport in materials and the one-particle reduced density matrices used to compute electric
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Constant gap between conventional strategies and those based on C*-dynamics for self-embezzlement Quantum (IF 6.439) Pub Date : 2022-07-07 Richard Cleve, Benoit Collins, Li Liu, Vern Paulsen
We consider a bipartite transformation that we call $self-embezzlement$ and use it to prove a constant gap between the capabilities of two models of quantum information: the conventional model, where bipartite systems are represented by tensor products of Hilbert spaces; and a natural model of quantum information processing for abstract states on C*-algebras, where joint systems are represented by
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Platonic Bell inequalities for all dimensions Quantum (IF 6.439) Pub Date : 2022-07-07 Károly F. Pál, Tamás Vértesi
In this paper we study the Platonic Bell inequalities for all possible dimensions. There are five Platonic solids in three dimensions, but there are also solids with Platonic properties (also known as regular polyhedra) in four and higher dimensions. The concept of Platonic Bell inequalities in the three-dimensional Euclidean space was introduced by Tavakoli and Gisin [Quantum 4, 293 (2020)]. For any
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Bounds on approximating Max $k$XOR with quantum and classical local algorithms Quantum (IF 6.439) Pub Date : 2022-07-07 Kunal Marwaha, Stuart Hadfield
We consider the power of local algorithms for approximately solving Max $k$XOR, a generalization of two constraint satisfaction problems previously studied with classical and quantum algorithms (MaxCut and Max E3LIN2). In Max $k$XOR each constraint is the XOR of exactly $k$ variables and a parity bit. On instances with either random signs (parities) or no overlapping clauses and $D+1$ clauses per variable
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Divide-and-conquer verification method for noisy intermediate-scale quantum computation Quantum (IF 6.439) Pub Date : 2022-07-07 Yuki Takeuchi, Yasuhiro Takahashi, Tomoyuki Morimae, Seiichiro Tani
Several noisy intermediate-scale quantum computations can be regarded as logarithmic-depth quantum circuits on a sparse quantum computing chip, where two-qubit gates can be directly applied on only some pairs of qubits. In this paper, we propose a method to efficiently verify such noisy intermediate-scale quantum computation. To this end, we first characterize small-scale quantum operations with respect
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The Quantum Approximate Optimization Algorithm and the Sherrington-Kirkpatrick Model at Infinite Size Quantum (IF 6.439) Pub Date : 2022-07-07 Edward Farhi, Jeffrey Goldstone, Sam Gutmann, Leo Zhou
The Quantum Approximate Optimization Algorithm (QAOA) is a general-purpose algorithm for combinatorial optimization problems whose performance can only improve with the number of layers $p$. While QAOA holds promise as an algorithm that can be run on near-term quantum computers, its computational power has not been fully explored. In this work, we study the QAOA applied to the Sherrington-Kirkpatrick
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Entangled subspaces and generic local state discrimination with pre-shared entanglement Quantum (IF 6.439) Pub Date : 2022-07-07 Benjamin Lovitz, Nathaniel Johnston
Walgate and Scott have determined the maximum number of generic pure quantum states that can be unambiguously discriminated by an LOCC measurement [Journal of Physics A: Mathematical and Theoretical, 41:375305, 08 2008]. In this work, we determine this number in a more general setting in which the local parties have access to pre-shared entanglement in the form of a resource state. We find that, for
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Quantum advantage using high-dimensional twisted photons as quantum finite automata Quantum (IF 6.439) Pub Date : 2022-06-30 Stephen Z. D. Plachta, Markus Hiekkamäki, Abuzer Yakaryılmaz, Robert Fickler
Quantum finite automata (QFA) are basic computational devices that make binary decisions using quantum operations. They are known to be exponentially memory efficient compared to their classical counterparts. Here, we demonstrate an experimental implementation of multi-qubit QFAs using the orbital angular momentum (OAM) of single photons. We implement different high-dimensional QFAs encoded on a single
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A game of quantum advantage: linking verification and simulation Quantum (IF 6.439) Pub Date : 2022-06-30 Daniel Stilck França, Raul Garcia-Patron
We present a formalism that captures the process of proving quantum superiority to skeptics as an interactive game between two agents, supervised by a referee. Bob, is sampling from a classical distribution on a quantum device that is supposed to demonstrate a quantum advantage. The other player, the skeptical Alice, is then allowed to propose mock distributions supposed to reproduce Bob's device's
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An improved quantum-inspired algorithm for linear regression Quantum (IF 6.439) Pub Date : 2022-06-30 András Gilyén, Zhao Song, Ewin Tang
We give a classical algorithm for linear regression analogous to the quantum matrix inversion algorithm [Harrow, Hassidim, and Lloyd, Physical Review Letters'09] for low-rank matrices [Wossnig, Zhao, and Prakash, Physical Review Letters'18], when the input matrix $A$ is stored in a data structure applicable for QRAM-based state preparation. Namely, suppose we are given an $A \in \mathbb{C}^{m\times
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Does causal dynamics imply local interactions? Quantum (IF 6.439) Pub Date : 2022-06-29 Zoltán Zimborás, Terry Farrelly, Szilárd Farkas, Lluis Masanes
We consider quantum systems with causal dynamics in discrete spacetimes, also known as quantum cellular automata (QCA). Due to time-discreteness this type of dynamics is not characterized by a Hamiltonian but by a one-time-step unitary. This can be written as the exponential of a Hamiltonian but in a highly non-unique way. We ask if any of the Hamiltonians generating a QCA unitary is local in some
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Multi-armed quantum bandits: Exploration versus exploitation when learning properties of quantum states Quantum (IF 6.439) Pub Date : 2022-06-29 Josep Lumbreras, Erkka Haapasalo, Marco Tomamichel
We initiate the study of tradeoffs between exploration and exploitation in online learning of properties of quantum states. Given sequential oracle access to an unknown quantum state, in each round, we are tasked to choose an observable from a set of actions aiming to maximize its expectation value on the state (the reward). Information gained about the unknown state from previous rounds can be used
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Quantum scattering as a work source Quantum (IF 6.439) Pub Date : 2022-06-29 Samuel L. Jacob, Massimiliano Esposito, Juan M. R. Parrondo, Felipe Barra
We consider a collision between a moving particle and a fixed system, each having internal degrees of freedom. We identify the regime where the motion of the particle acts as a work source for the joint internal system, leading to energy changes which preserve the entropy. This regime arises when the particle has high kinetic energy and its quantum state of motion is broad in momentum and narrow in
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Classical simulations of communication channels Quantum (IF 6.439) Pub Date : 2022-06-29 Péter E. Frenkel
We investigate whether certain non-classical communication channels can be simulated by a classical channel with a given number of states and a given `amount' of noise. It is proved that any noisy quantum channel can be simulated by a corresponding classical channel with `the same amount' of noise. Classical simulations of general probabilistic channels are also studied.
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BROTOCs and Quantum Information Scrambling at Finite Temperature Quantum (IF 6.439) Pub Date : 2022-06-27 Namit Anand, Paolo Zanardi
Out-of-time-ordered correlators (OTOCs) have been extensively studied in recent years as a diagnostic of quantum information scrambling. In this paper, we study quantum information-theoretic aspects of the regularized finite-temperature OTOC. We introduce analytical results for the bipartite regularized OTOC (BROTOC): the regularized OTOC averaged over random unitaries supported over a bipartition
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Deep Reinforcement Learning for Quantum State Preparation with Weak Nonlinear Measurements Quantum (IF 6.439) Pub Date : 2022-06-28 Riccardo Porotti, Antoine Essig, Benjamin Huard, Florian Marquardt
Quantum control has been of increasing interest in recent years, e.g. for tasks like state initialization and stabilization. Feedback-based strategies are particularly powerful, but also hard to find, due to the exponentially increased search space. Deep reinforcement learning holds great promise in this regard. It may provide new answers to difficult questions, such as whether nonlinear measurements
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Limits of Short-Time Evolution of Local Hamiltonians Quantum (IF 6.439) Pub Date : 2022-06-27 Ali Hamed Moosavian, Seyed Sajad Kahani, Salman Beigi
Evolutions of local Hamiltonians in short times are expected to remain local and thus limited. In this paper, we validate this intuition by proving some limitations on short-time evolutions of local time-dependent Hamiltonians. We show that the distribution of the measurement output of short-time (at most logarithmic) evolutions of local Hamiltonians are $concentrated$ and satisfy an $\textit{isoperimetric
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Low depth algorithms for quantum amplitude estimation Quantum (IF 6.439) Pub Date : 2022-06-27 Tudor Giurgica-Tiron, Iordanis Kerenidis, Farrokh Labib, Anupam Prakash, William Zeng
We design and analyze two new low depth algorithms for amplitude estimation (AE) achieving an optimal tradeoff between the quantum speedup and circuit depth. For $\beta \in (0,1]$, our algorithms require $N= \tilde{O}( \frac{1}{ \epsilon^{1+\beta}})$ oracle calls and require the oracle to be called sequentially $D= O( \frac{1}{ \epsilon^{1-\beta}})$ times to perform amplitude estimation within additive
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Thermometry of Gaussian quantum systems using Gaussian measurements Quantum (IF 6.439) Pub Date : 2022-06-23 Marina F.B. Cenni, Ludovico Lami, Antonio Acín, Mohammad Mehboudi
We study the problem of estimating the temperature of Gaussian systems with feasible measurements, namely Gaussian and photo-detection-like measurements. For Gaussian measurements, we develop a general method to identify the optimal measurement numerically, and derive the analytical solutions in some relevant cases. For a class of single-mode states that includes thermal ones, the optimal Gaussian
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BROTOCs and Quantum Information Scrambling at Finite Temperature Quantum (IF 6.439) Pub Date : 2022-06-23 Namit Anand, Paolo Zanardi
Out-of-time-ordered correlators (OTOCs) have been extensively studied in recent years as a diagnostic of quantum information scrambling. In this paper, we study quantum information-theoretic aspects of the $regularized$ finite-temperature OTOC. We introduce analytical results for the $\textit{bipartite regularized}$ OTOC (BROTOC): the regularized OTOC averaged over random unitaries supported over a
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Topological Link Models of Multipartite Entanglement Quantum (IF 6.439) Pub Date : 2022-06-20 Ning Bao, Newton Cheng, Sergio Hernández-Cuenca, Vincent Paul Su
We introduce a novel model of multipartite entanglement based on topological links, generalizing the graph/hypergraph entropy cone program. We demonstrate that there exist link representations of entropy vectors which provably cannot be represented by graphs or hypergraphs. Furthermore, we show that the contraction map proof method generalizes to the topological setting, though now requiring oracular
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Universal quantum circuits for quantum chemistry Quantum (IF 6.439) Pub Date : 2022-06-20 Juan Miguel Arrazola, Olivia Di Matteo, Nicolás Quesada, Soran Jahangiri, Alain Delgado, Nathan Killoran
Universal gate sets for quantum computing have been known for decades, yet no universal gate set has been proposed for particle-conserving unitaries, which are the operations of interest in quantum chemistry. In this work, we show that controlled single-excitation gates in the form of Givens rotations are universal for particle-conserving unitaries. Single-excitation gates describe an arbitrary $U(2)$
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Inverse engineering of fast state transfer among coupled oscillators Quantum (IF 6.439) Pub Date : 2022-06-20 Xiao-Jing Lu, Ion Lizuain, J. G. Muga
We design faster-than-adiabatic state transfers (switching of quantum numbers) in time-dependent coupled-oscillator Hamiltonians. The manipulation to drive the process is found using a two-dimensional invariant recently proposed in S. Simsek and F. Mintert, Quantum 5 (2021) 409, and involves both rotation and transient scaling of the principal axes of the potential in a Cartesian representation. Importantly
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Quantum simulation in the semi-classical regime Quantum (IF 6.439) Pub Date : 2022-06-17 Shi Jin, Xiantao Li, Nana Liu
Solving the time-dependent Schrödinger equation is an important application area for quantum algorithms. We consider Schrödinger's equation in the semi-classical regime. Here the solutions exhibit strong multiple-scale behavior due to a small parameter $\hbar$, in the sense that the dynamics of the quantum states and the induced observables can occur on different spatial and temporal scales. Such a
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One bound to rule them all: from Adiabatic to Zeno Quantum (IF 6.439) Pub Date : 2022-06-14 Daniel Burgarth, Paolo Facchi, Giovanni Gramegna, Kazuya Yuasa
We derive a universal nonperturbative bound on the distance between unitary evolutions generated by time-dependent Hamiltonians in terms of the difference of their integral actions. We apply our result to provide explicit error bounds for the rotating-wave approximation and generalize it beyond the qubit case. We discuss the error of the rotating-wave approximation over long time and in the presence
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Emergent quantum state designs and biunitarity in dual-unitary circuit dynamics Quantum (IF 6.439) Pub Date : 2022-06-15 Pieter W. Claeys, Austen Lamacraft
Recent works have investigated the emergence of a new kind of random matrix behaviour in unitary dynamics following a quantum quench. Starting from a time-evolved state, an ensemble of pure states supported on a small subsystem can be generated by performing projective measurements on the remainder of the system, leading to a $\textit{projected ensemble}$. In chaotic quantum systems it was conjectured
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Genuine multipartite entanglement of quantum states in the multiple-copy scenario Quantum (IF 6.439) Pub Date : 2022-06-13 Carlos Palazuelos, Julio I. de Vicente
Genuine multipartite entanglement (GME) is considered a powerful form of entanglement since it corresponds to those states that are not biseparable, i.e. a mixture of partially separable states across different bipartitions of the parties. In this work we study this phenomenon in the multiple-copy regime, where many perfect copies of a given state can be produced and controlled. In this scenario the
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Integrability of the $ν=4/3$ fractional quantum Hall edge states Quantum (IF 6.439) Pub Date : 2022-06-14 Yichen Hu, Biao Lian
We investigate the homogeneous chiral edge theory of the filling $\nu=4/3$ fractional quantum Hall state, which is parameterized by a Luttinger liquid velocity matrix and an electron tunneling amplitude (ignoring irrelevant terms). We identify two solvable cases: one case where the theory gives two free chiral boson modes, and the other case where the theory yields one free charge $\frac{2e}{\sqrt{3}}$
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The Classification of Clifford Gates over Qubits Quantum (IF 6.439) Pub Date : 2022-06-13 Daniel Grier, Luke Schaeffer
We examine the following problem: given a collection of Clifford gates, describe the set of unitaries generated by circuits composed of those gates. Specifically, we allow the standard circuit operations of composition and tensor product, as well as ancillary workspace qubits as long as they start and end in states uncorrelated with the input, which rule out common "magic state injection" techniques
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Non-ergodic delocalized phase with Poisson level statistics Quantum (IF 6.439) Pub Date : 2022-06-09 Weichen Tang, Ivan M. Khaymovich
Motivated by the many-body localization (MBL) phase in generic interacting disordered quantum systems, we develop a model simulating the same eigenstate structure like in MBL, but in the random-matrix setting. Demonstrating the absence of energy level repulsion (Poisson statistics), this model carries non-ergodic eigenstates, delocalized over the extensive number of configurations in the Hilbert space
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Architecture aware compilation of quantum circuits via lazy synthesis Quantum (IF 6.439) Pub Date : 2022-06-07 Simon Martiel, Timothée Goubault de Brugière
Qubit routing is a key problem for quantum circuit compilation. It consists in rewriting a quantum circuit by adding the least possible number of instructions to make the circuit compliant with some architecture's connectivity constraints. Usually, this problem is tackled via either SWAP insertion techniques or re-synthesis of portions of the circuit using architecture aware synthesis algorithms. In
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A variational quantum algorithm for the Feynman-Kac formula Quantum (IF 6.439) Pub Date : 2022-06-07 Hedayat Alghassi, Amol Deshmukh, Noelle Ibrahim, Nicolas Robles, Stefan Woerner, Christa Zoufal
We propose an algorithm based on variational quantum imaginary time evolution for solving the Feynman-Kac partial differential equation resulting from a multidimensional system of stochastic differential equations. We utilize the correspondence between the Feynman-Kac partial differential equation (PDE) and the Wick-rotated Schrödinger equation for this purpose. The results for a $(2+1)$ dimensional
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Topological phonons in arrays of ultracold dipolar particles Quantum (IF 6.439) Pub Date : 2022-06-07 Marco Di Liberto, Andreas Kruckenhauser, Peter Zoller, Mikhail A. Baranov
The notion of topology in physical systems is associated with the existence of a nonlocal ordering that is insensitive to a large class of perturbations. This brings robustness to the behaviour of the system and can serve as a ground for developing new fault-tolerant applications. We discuss how to design and study a large variety of topology-related phenomena for phonon-like collective modes in arrays
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Solvable Criterion for the Contextuality of any Prepare-and-Measure Scenario Quantum (IF 6.439) Pub Date : 2022-06-07 Victor Gitton, Mischa P. Woods
Starting from arbitrary sets of quantum states and measurements, referred to as the prepare-and-measure scenario, an operationally noncontextual ontological model of the quantum statistics associated with the prepare-and-measure scenario is constructed. The operationally noncontextual ontological model coincides with standard Spekkens noncontextual ontological models for tomographically complete scenarios
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Solving the Bose-Hubbard model in new ways Quantum (IF 6.439) Pub Date : 2022-06-02 Artur Sowa, Jonas Fransson
We introduce a new method for analysing the Bose-Hubbard model for an array of bosons with nearest neighbor interactions. It is based on a number-theoretic implementation of the creation and annihilation operators that constitute the model. One of the advantages of this approach is that it facilitates accurate computations involving multi-particle states. In particular, we provide a rigorous computer
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One-Shot Hybrid State Redistribution Quantum (IF 6.439) Pub Date : 2022-05-30 Eyuri Wakakuwa, Yoshifumi Nakata, Min-Hsiu Hsieh
We consider state redistribution of a "hybrid" information source that has both classical and quantum components. The sender transmits classical and quantum information at the same time to the receiver, in the presence of classical and quantum side information both at the sender and at the decoder. The available resources are shared entanglement, and noiseless classical and quantum communication channels
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A device-independent protocol for XOR oblivious transfer Quantum (IF 6.439) Pub Date : 2022-05-30 Srijita Kundu, Jamie Sikora, Ernest Y.-Z. Tan
Oblivious transfer is a cryptographic primitive where Alice has two bits and Bob wishes to learn some function of them. Ideally, Alice should not learn Bob's desired function choice and Bob should not learn any more than what is logically implied by the function value. While decent quantum protocols for this task are known, many become completely insecure if an adversary were to control the quantum
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A general quantum algorithm for open quantum dynamics demonstrated with the Fenna-Matthews-Olson complex Quantum (IF 6.439) Pub Date : 2022-05-30 Zixuan Hu, Kade Head-Marsden, David A. Mazziotti, Prineha Narang, Sabre Kais
Using quantum algorithms to simulate complex physical processes and correlations in quantum matter has been a major direction of quantum computing research, towards the promise of a quantum advantage over classical approaches. In this work we develop a generalized quantum algorithm to simulate any dynamical process represented by either the operator sum representation or the Lindblad master equation
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Quantum Machine Learning with SQUID Quantum (IF 6.439) Pub Date : 2022-05-30 Alessandro Roggero, Jakub Filipek, Shih-Chieh Hsu, Nathan Wiebe
In this work we present the Scaled QUantum IDentifier (SQUID), an open-source framework for exploring hybrid Quantum-Classical algorithms for classification problems. The classical infrastructure is based on PyTorch and we provide a standardized design to implement a variety of quantum models with the capability of back-propagation for efficient training. We present the structure of our framework and
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Metrology-assisted entanglement distribution in noisy quantum networks Quantum (IF 6.439) Pub Date : 2022-05-27 Simon Morelli, David Sauerwein, Michalis Skotiniotis, Nicolai Friis
We consider the distribution of high-dimensional entangled states to multiple parties via noisy channels and the subsequent probabilistic conversion of these states to desired target states using stochastic local operations and classical communication. We show that such state-conversion protocols can be enhanced by embedded channel-estimation routines at no additional cost in terms of the number of
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Universal Entanglement Transitions of Free Fermions with Long-range Non-unitary Dynamics Quantum (IF 6.439) Pub Date : 2022-05-27 Pengfei Zhang, Chunxiao Liu, Shao-Kai Jian, Xiao Chen
Non-unitary evolution can give rise to novel steady states classified by their entanglement properties. In this work, we aim to understand the effect of long-range hopping that decays with $r^{-\alpha}$ in non-Hermitian free-fermion systems. We first study two solvable Brownian models with long-range non-unitary dynamics: a large-$N$ SYK$_2$ chain and a single-flavor fermion chain and we show that
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Quantum Bell inequalities from Information Causality – tight for Macroscopic Locality Quantum (IF 6.439) Pub Date : 2022-05-24 Mariami Gachechiladze, Bartłomiej Bąk, Marcin Pawłowski, Nikolai Miklin
In a Bell test, the set of observed probability distributions complying with the principle of local realism is fully characterized by Bell inequalities. Quantum theory allows for a violation of these inequalities, which is famously regarded as Bell nonlocality. However, finding the maximal degree of this violation is, in general, an undecidable problem. Consequently, no algorithm can be used to derive
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Receiver-Device-Independent Quantum Key Distribution Quantum (IF 6.439) Pub Date : 2022-05-24 Marie Ioannou, Maria Ana Pereira, Davide Rusca, Fadri Grünenfelder, Alberto Boaron, Matthieu Perrenoud, Alastair A. Abbott, Pavel Sekatski, Jean-Daniel Bancal, Nicolas Maring, Hugo Zbinden, Nicolas Brunner
We present protocols for quantum key distribution in a prepare-and-measure setup with an asymmetric level of trust. While the device of the sender (Alice) is partially characterized, the receiver's (Bob's) device is treated as a black-box. The security of the protocols is based on the assumption that Alice's prepared states have limited overlaps, but no explicit bound on the Hilbert space dimension
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Analytical framework for non-equilibrium phase transition to Bose–Einstein condensate Quantum (IF 6.439) Pub Date : 2022-05-24 V. Yu. Shishkov, E. S. Andrianov, Yu. E. Lozovik
The theoretical description of non-equilibrium Bose–Einstein condensate (BEC) is one of the main challenges in modern statistical physics and kinetics. The non-equilibrium nature of BEC makes it impossible to employ the well-established formalism of statistical mechanics. We develop a framework for the analytical description of a non-equilibrium phase transition to BEC that, in contrast to previously
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Quantum agents in the Gym: a variational quantum algorithm for deep Q-learning Quantum (IF 6.439) Pub Date : 2022-05-24 Andrea Skolik, Sofiene Jerbi, Vedran Dunjko
Quantum machine learning (QML) has been identified as one of the key fields that could reap advantages from near-term quantum devices, next to optimization and quantum chemistry. Research in this area has focused primarily on variational quantum algorithms (VQAs), and several proposals to enhance supervised, unsupervised and reinforcement learning (RL) algorithms with VQAs have been put forward. Out
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Numerical Implementation of Just-In-Time Decoding in Novel Lattice Slices Through the Three-Dimensional Surface Code Quantum (IF 6.439) Pub Date : 2022-05-24 T. R. Scruby, D. E. Browne, P. Webster, M. Vasmer
We build on recent work by B. Brown (Sci. Adv. 6, eaay4929 (2020)) to develop and simulate an explicit recipe for a just-in-time decoding scheme in three 3D surface codes, which can be used to implement a transversal (non-Clifford) $\overline{CCZ}$ between three 2D surface codes in time linear in the code distance. We present a fully detailed set of bounded-height lattice slices through the 3D codes