Observation of Time-Invariant Coherence in a Nuclear Magnetic Resonance Quantum Simulator

Silva, Isabela A.; Souza, Alexandre M.; Bromley, Thomas R.; Cianciaruso, Marco; Marx, Raimund; Sarthour, R. S.; Franco, Rosario Lo; Glaser, Steffen J.; deAzevedo, Eduardo R.; Soares-Pinto, Diogo O.; Adesso, Gerardo

doi:10.1103/physrevlett.117.160402

Cited by 100 publications

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“…This fascinating behavior was named the phenomenon of sudden transition from classical to quantum decoherence. These intriguing behaviors of freezing and sudden transition were further explored theoretically and verified experimentally [19][20][21][22][23]. Consequently, it was demonstrated that the type of initial states which exhibit such as non-trivial behaviors rely upon the feature of the decohering environment being considered.…”

Section: Introductionmentioning

confidence: 83%

Controlling sudden transition from classical to quantum decoherence via non-equilibrium environments

et al. 2020

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We investigate the freezing and sudden transition in the dynamical behavior of quantum and classical correlations in a system composed of two identical non-interacting qubits locally subjected to their own non-equilibrium environments. In contrast to the equilibrium case, one can observe striking results when a bipartite quantum system couples with the non-equilibrium dephasing environment with non-stationary and non-Markovian features. Remarkably, the finite time interval in which the quantum correlation remains impervious to decoherence can be further prolonged as the environment deviates from equilibrium. This reveals that the non-equilibrium parameter provides an alternative tool to efficiently control the appearance of a sudden transition in the decay rates of correlations and their immunity towards the decoherence. Furthermore, for certain initial states, the appearance of another time-interval over which quantum correlation remains constant and the revival of classical correlation not only depends on the non-Markovianity but also on the non-equilibrium parameter.

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Section: Introductionmentioning

confidence: 83%

Controlling sudden transition from classical to quantum decoherence via non-equilibrium environments

et al. 2020

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“…These requirements are significant, but much easier than demanding direct control over two qubit operations, and correspond to the stateof-the-art in systems involving trapped ions [18][19][20], cold atoms [21,22], NMR [23][24][25] or superconducting circuits [26,27]. In these systems there already exist quantum simulators powerful enough to do simulations, and satisfy our requirements, but are not currently usable as computers as it is not known how to perform logic gates on them [2,4].…”

Section: The Schemementioning

confidence: 99%

In situ upgrade of quantum simulators to universal computers

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et al. 2018

Quantum

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Quantum simulators, machines that can replicate the dynamics of quantum systems, are being built as useful devices and are seen as a stepping stone to universal quantum computers. A key difference between the two is that computers have the ability to perform the logic gates that make up algorithms. We propose a method for learning how to construct these gates efficiently by using the simulator to perform optimal control on itself. This bypasses two major problems of purely classical approaches to the control problem: the need to have an accurate model of the system, and a classical computer more powerful than the quantum one to carry out the required simulations. Strong evidence that the scheme scales polynomially in the number of qubits, for systems of up to 9 qubits with Ising interactions, is presented from numerical simulations carried out in different topologies. This suggests that this in situ approach is a practical way of upgrading quantum simulators to computers.Recent and ongoing work on building large quantum systems is leading to simulators that are able to model physical phenomena, allowing questions about the underlying science to be answered [1][2][3]. These machines contain a register of quantum particles, typically two level quantum systems (qubits) storing quantum information. The presence of interactions between these leads to dynamics that, by varying control parameters in the system Hamiltonian, can replicate the quantum behaviour of systems of interest. This, however, is less general than a quantum computer which is able is to perform a universal set of logic gates on the qubits [4].Provided some control parameters can be varied in time, it is in principle possible to do an arbitrary gate on a quantum many-body system such as a quantum simulator [5][6][7]. Finding the right time-dependency however relies almost exclusively on numerical methods, especially when physical constraints on the control fields are taken into account [8,9]. These methods require a very precise knowledge of the parameters of a system, a daunting task for a machine with a huge number of degrees of freedom. Furthermore, they are intractable on a classical computer if the quantum simulator we want to solve the problem for is large enough to do something beyond the capabilities of classical computers. These two difficulties provide a major obstacle in using quantum simulators to perform arbitrary computation.We circumvent these problems by showing how well-known existing numerical methods can be translated to run in situ on the quantum simulator itself, as illustrated in Fig.1. A mix of an-

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“…In our experiment, the two-qubit system was encoded on 1 H and 13 C spin-1/2 nuclei in a chloroform (CHCl 3 ) enriched with a 13 C sample, allowing complete control of the amplitude and phase of each qubit separately [61][62][63]. Applying the pseudopure-state technique [1,[64][65][66][67], the family of states in Eq.…”

Section: Fig 1 Comparison Of the Ip P A (ρ Ab ) Versus The Ie Aliamentioning

confidence: 99%

There is more to quantum interferometry than entanglement

et al. 2017

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Entanglement has long stood as one of the characteristic features of quantum mechanics, yet recent developments have emphasized the importance of quantumness beyond entanglement for quantum foundations and technologies. We demonstrate that entanglement cannot entirely capture the worst-case sensitivity in quantum interferometry when quantum probes are used to estimate the phase imprinted by a Hamiltonian, with fixed energy levels but variable eigenbasis, acting on one arm of an interferometer. This is shown by defining a bipartite entanglement monotone tailored to this interferometric setting and proving that it never exceeds the so-called interferometric power, a quantity which relies on more general quantum correlations beyond entanglement and captures the relevant resource. We then prove that the interferometric power can never increase when local commutativity-preserving operations are applied to qubit probes, an important step to validate such a quantity as a genuine quantum correlations monotone. These findings are accompanied by a room-temperature nuclear magnetic resonance experimental investigation, in which two-qubit states with extremal (maximal and minimal) interferometric power at fixed entanglement are produced and characterized.

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Observation of Time-Invariant Coherence in a Nuclear Magnetic Resonance Quantum Simulator

Cited by 100 publications

References 64 publications

Controlling sudden transition from classical to quantum decoherence via non-equilibrium environments

Controlling sudden transition from classical to quantum decoherence via non-equilibrium environments

In situ upgrade of quantum simulators to universal computers

There is more to quantum interferometry than entanglement

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