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Quantum kernels quantify similarity between data points by measuring the inner product between quantum states, computed through quantum circuit measurements. By embedding data into quantum systems, quantum kernel feature maps, that may be…

Quantum Physics · Physics 2025-03-24 Joachim Tomasi , Sandrine Anthoine , Hachem Kadri

We study multifractal properties in time evolution of a single particle subject to repeated measurements. For quantum systems, we consider circuit models consisting of local unitary gates and local projective measurements. For classical…

Quantum Physics · Physics 2024-10-28 Kohei Yajima , Hisanori Oshima , Ken Mochizuki , Yohei Fuji

As the hardware technology for quantum computing advances, its possible applications are actively searched and developed. However, such applications still suffer from the noise on quantum devices, in particular when using two-qubit gates…

Quantum Physics · Physics 2021-02-03 Kosuke Mitarai , Keisuke Fujii

The dependence of the dynamics of open quantum systems upon initial correlations between the system and environment is an utterly important yet poorly understood subject. For technical convenience most prior studies assume factorizable…

Quantum Physics · Physics 2011-08-05 C. H. Fleming , B. L. Hu , Albert Roura

The unitary generation of coherence from an incoherent thermal state is investigated. We consider a completely controllable Hamiltonian allowing to generate all possible unitary transformations. Optimizing the unitary control to achieve…

Quantum Physics · Physics 2019-10-02 Shimshon Kallush , Aviv Aroch , Ronnie Kosloff

It is shown that the fidelity of the dynamically evolved system with its earlier time density matrix provides a signature of non-Markovian dynamics. Also, the fidelity associated with the initial state and the dynamically evolved state is…

Quantum Physics · Physics 2010-10-28 A K Rajagopal , A R Usha Devi , R W Rendell

We study the problem of universal quantum cloning -- taking several identical copies of a pure but unknown quantum state and producing further copies. While it is well known that it is impossible to perfectly reproduce the state, how well…

Quantum Physics · Physics 2016-08-09 Alastair Kay

Quantum algorithms for probing ground-state properties of quantum systems require good initial states. Projection-based methods such as eigenvalue filtering rely on inputs that have a significant overlap with the low-energy subspace, which…

Quantum Physics · Physics 2024-04-10 Danial Motlagh , Modjtaba Shokrian Zini , Juan Miguel Arrazola , Nathan Wiebe

The effect of a local instantaneous quantum dynamical process (QDP), either unitary or non-unitary, on the quantum state transfer through a unitary Hamiltonian evolution is investigated for both integrable and non-integrable dynamics. There…

Quantum Physics · Physics 2018-12-26 Saikat Sur , V. Subrahmanyam

The nonrelativistic limit of nonlocal modifications to the Klein Gordon operator is studied, and the experimental possibilities of casting stringent constraints on the nonlocality scale via planned and/or current optomechanical experiments…

General Relativity and Quantum Cosmology · Physics 2017-02-01 Alessio Belenchia , Dionigi M. T. Benincasa , Stefano Liberati , Francesco Marin , Francesco Marino , Antonello Ortolan

In this paper we return to the problem of reduced-state dynamics in the presence of an interacting environment. The question we investigate is how to appropriately model a particular system evolution given some knowledge of the…

Quantum Physics · Physics 2015-07-02 Eric Chitambar , Ali Abu-Nada , Russell Ceballos , Mark Byrd

Quantum control in large dimensional Hilbert spaces is essential for realizing the power of quantum information processing. For closed quantum systems the relevant input/output maps are unitary transformations, and the fundamental challenge…

Quantum Physics · Physics 2014-10-17 B. E. Anderson , H. Sosa-Martinez , C. A. Riofrío , I. H. Deutsch , P. S. Jessen

Starting from a state of low quantum entanglement, local unitary time evolution increases the entanglement of a quantum many-body system. In contrast, local projective measurements disentangle degrees of freedom and decrease entanglement.…

Statistical Mechanics · Physics 2019-07-24 Amos Chan , Rahul M. Nandkishore , Michael Pretko , Graeme Smith

A novel scheme to simulate the evolution of a restricted set of observables of a quantum system is proposed. The set comprises the spectrum-generating algebra of the Hamiltonian. The idea is to consider a certain open-system evolution,…

Quantum Physics · Physics 2009-11-13 M. Khasin , R. Kosloff

We compare two approaches to non-Markovian quantum evolution: one based on the concept of divisible maps and the other one based on distinguishability of quantum states. The former concept is fully characterized in terms of local generator…

Quantum Physics · Physics 2013-04-30 Dariusz Chruściński , Filip A. Wudarski

We address measurement-based generation of quantum coherence in continuous variable systems. We consider Gaussian measurements performed on Gaussian states and focus on two scenarios. In the first one, we assume an initially correlated…

Quantum Physics · Physics 2017-08-14 Francesco Albarelli , Marco G. Genoni , Matteo G. A. Paris

We propose a measure of nonclassical correlation $N_{\mathcal F}^{\mathcal G}$ in terms of local Gaussian unitary operations based on square of the fidelity $\mathcal F$ for bipartite continuous-variable systems. This quantity is easier to…

Quantum Physics · Physics 2019-02-01 Liang Liu , Xiaofei Qi , Jinchuan Hou

Realizing the theoretical promise of quantum computers will require overcoming decoherence. Here we demonstrate numerically that high fidelity quantum gates are possible within a framework of quantum dynamical decoupling. Orders of…

Quantum Physics · Physics 2010-12-16 Jacob R. West , Daniel A. Lidar , Bryan H. Fong , Mark F. Gyure

In a digital quantum simulator, basic two-qubit interactions are manipulated by means of fast local control operations to establish a desired target Hamiltonian. Here we consider a quantum simulator based on logical systems, i.e. where…

Quantum Physics · Physics 2023-02-08 Ferran Riera-Sàbat , Pavel Sekatski , Wolfgang Dür

The inhibition of the decay of a quantum system by frequent measurements is known as quantum Zeno effect. Beyond the limit of projective measurements, the interplay between the unitary dynamics of the system and the coupling to a…

Quantum Physics · Physics 2015-10-09 Andreas Prinz-Zwick , Gert-Ludwig Ingold , Peter Talkner