Quantum operation
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Adiabatic quantum computation Open
Adiabatic quantum computing (AQC) started as an approach to solving optimization problems, and has evolved into an important universal alternative to the standard circuit model of quantum computing, with deep connections to both classical …
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Quantum Machine Learning in Feature Hilbert Spaces Open
A basic idea of quantum computing is surprisingly similar to that of kernel methods in machine learning, namely, to efficiently perform computations in an intractably large Hilbert space. In this Letter we explore some theoretical foundati…
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Bifurcation-based adiabatic quantum computation with a nonlinear oscillator network Open
The dynamics of nonlinear systems qualitatively change depending on their parameters, which is called bifurcation. A quantum-mechanical nonlinear oscillator can yield a quantum superposition of two oscillation states, known as a Schrödinge…
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The role of quantum measurement in stochastic thermodynamics Open
This article sets up a new formalism to investigate stochastic thermodynamics in the quantum regime, where stochasticity and irreversibility primarily come from quantum measurement. In the absence of any bath, we define a purely quantum co…
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Quantum Common Causes and Quantum Causal Models Open
Reichenbach’s principle asserts that if two observed variables are found to be correlated, then there should be a causal explanation of these correlations. Furthermore, if the explanation is in terms of a common cause, then the conditional…
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Quantum theory based on real numbers can be experimentally falsified Open
Although complex numbers are essential in mathematics, they are not needed to describe physical experiments, as those are expressed in terms of probabilities, hence real numbers. Physics, however, aims to explain, rather than describe, exp…
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Simulating Positive-Operator-Valued Measures with Projective Measurements Open
Standard projective measurements (PMs) represent a subset of all possible measurements in quantum physics, defined by positive-operator-valued measures. We study what quantum measurements are projective simulable, that is, can be simulated…
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Quantum Speed Limits across the Quantum-to-Classical Transition Open
Quantum speed limits set an upper bound to the rate at which a quantum system can evolve. Adopting a phase-space approach, we explore quantum speed limits across the quantum-to-classical transition and identify equivalent bounds in the cla…
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Unraveling the Large Deviation Statistics of Markovian Open Quantum Systems Open
We analyze dynamical large deviations of quantum trajectories in Markovian open quantum systems in their full generality. We derive a quantum level-2.5 large deviation principle for these systems, which describes the joint fluctuations of …
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Quantifying Quantum Resources with Conic Programming Open
Resource theories can be used to formalize the quantification and manipulation of resources in quantum information processing such as entanglement, asymmetry and coherence of quantum states, and incompatibility of quantum measurements. Giv…
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Contextuality as a Resource for Models of Quantum Computation with Qubits Open
A central question in quantum computation is to identify the resources that are responsible for quantum speed-up. Quantum contextuality has been recently shown to be a resource for quantum computation with magic states for odd-prime dimens…
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Speed limit for open quantum systems Open
We study the quantum speed limit for open quantum systems described by the Lindblad master equation. The obtained inequality shows a trade-off relation between the operation time and the physical quantities such as the energy fluctuation a…
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Relations between topology and the quantum metric for Chern insulators Open
We investigate relations between topology and the quantum metric of two-dimensional Chern insulators. The quantum metric is the Riemannian metric defined on a parameter space induced from quantum states. Similar to the Berry curvature, the…
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Self-testing quantum states and measurements in the prepare-and-measure scenario Open
The goal of self-testing is to characterize an a priori unknown quantum\nsystem based solely on measurement statistics, i.e. using an uncharacterized\nmeasurement device. Here we develop self-testing methods for quantum\nprepare-and-measur…
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Quantum Simulation of Open Quantum Systems Using a Unitary Decomposition of Operators Open
Electron transport in realistic physical and chemical systems often involves the nontrivial exchange of energy with a large environment, requiring the definition and treatment of open quantum systems. Because the time evolution of an open …
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Models of Quantum Complexity Growth Open
The concept of quantum complexity has far-reaching implications spanning\ntheoretical computer science, quantum many-body physics, and high energy\nphysics. The quantum complexity of a unitary transformation or quantum state is\ndefined as…
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Quantum simulation of hyperbolic space with circuit quantum electrodynamics: From graphs to geometry Open
We show how quantum many-body systems on hyperbolic lattices with nearest-neighbor hopping and local interactions can be mapped onto quantum field theories in continuous negatively curved space. The underlying lattices have recently been r…
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Ruling Out Real-Valued Standard Formalism of Quantum Theory Open
Standard quantum theory was formulated with complex-valued Schrödinger equations, wave functions, operators, and Hilbert spaces. Previous work attempted to simulate quantum systems using only real numbers by exploiting an enlarged Hilbert …
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Work Fluctuations in Slow Processes: Quantum Signatures and Optimal Control Open
An important result in classical stochastic thermodynamics is the work fluctuation-dissipation relation (FDR), which states that the dissipated work done along a slow process is proportional to the resulting work fluctuations. We show that…
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Universal variational quantum computation Open
Variational quantum algorithms dominate contemporary gate-based quantum\nenhanced optimisation, eigenvalue estimation and machine learning. Here we\nestablish the quantum computational universality of variational quantum\ncomputation by de…
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Evolution equation for quantum coherence Open
The estimation of the decoherence process of an open quantum system is of both theoretical significance and experimental appealing. Practically, the decoherence can be easily estimated if the coherence evolution satisfies some simple relat…
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Quantum Fluctuation Theorems beyond Two-Point Measurements Open
We derive detailed and integral quantum fluctuation theorems for heat exchange in a quantum correlated bipartite thermal system using the framework of dynamic Bayesian networks. Contrary to the usual two-projective-measurement scheme that …
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Simple expression for the quantum Fisher information matrix Open
Quantum Fisher information matrix (QFIM) is a cornerstone of modern quantum\nmetrology and quantum information geometry. Apart from optimal estimation, it\nfinds applications in description of quantum speed limits, quantum criticality,\nqu…
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Resource Theory of Coherence Based on Positive-Operator-Valued Measures Open
Quantum coherence is a fundamental feature of quantum mechanics and an underlying requirement for most quantum information tasks. In the resource theory of coherence, incoherent states are diagonal with respect to a fixed orthonormal basis…
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Tight, robust, and feasible quantum speed limits for open dynamics Open
Starting from a geometric perspective, we derive a quantum speed limit for arbitrary open quantum evolution, which could be Markovian or non-Markovian, providing a fundamental bound on the time taken for the most general quantum dynamics. …
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Gaussian Hypothesis Testing and Quantum Illumination Open
Quantum hypothesis testing is one of the most basic tasks in quantum information theory and has fundamental links with quantum communication and estimation theory. In this paper, we establish a formula that characterizes the decay rate of …
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Self-testing nonprojective quantum measurements in prepare-and-measure experiments Open
Generalized measurements on quantum systems can be characterized with only small control of laboratory devices.
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Autonomous quantum machines and the finite sized Quasi-Ideal clock Open
Processes such as quantum computation, or the evolution of quantum cellular automata are typically described by a unitary operation implemented by an external observer. In particular, an interaction is generally turned on for a precise amo…
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Masking Quantum Information is Impossible Open
Classical information encoded in composite quantum states can be completely hidden from the reduced subsystems and may be found only in the correlations. Can the same be true for quantum information? If quantum information is hidden from s…
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Reversing Unknown Quantum Transformations: Universal Quantum Circuit for Inverting General Unitary Operations Open
Given a quantum gate implementing a d-dimensional unitary operation U_{d}, without any specific description but d, and permitted to use k times, we present a universal probabilistic heralded quantum circuit that implements the exact invers…