Characterization of qubit chains by Feynman probes

Tamascelli, Dario; Benedetti, Claudia; Olivares, Stefano; Paris, Matteo G. A.

doi:10.1103/physreva.94.042129

Cited by 46 publications

(37 citation statements)

References 59 publications

(76 reference statements)

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“…where A x,t and B x,t are the amplitudes of the states |↑ and |↓ at position x at time t, respectively. The A, B coefficients are in turn linked by the iterative relations 50,50]. In both cases the initial state of the system has been set to 1…”

Section: Evolution In Discrete-time Quantum Walkmentioning

confidence: 99%

Quantum walker as a probe for its coin parameter

2019

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In discrete-time quantum walk (DTQW) the walker's coin space entangles with the position space after the very first step of the evolution. This phenomenon may be exploited to obtain the value of the coin parameter θ by performing measurements on the sole position space of the walker. In this paper, we evaluate the ultimate quantum limits to precision for this class of estimation protocols, and use this result to assess measurement schemes having limited access to the position space of the walker in one dimension. We find that the quantum Fisher information (QFI) of the walker's position space Hw(θ) increases with θ and with time which, in turn, may be seen as a metrological resource. We also find a difference in the QFI of bounded and unbounded DTQWs, and provide an interpretation of the different behaviors in terms of interference in the position space. Finally, we compare Hw(θ) to the full QFI H f (θ), i.e., the QFI of the walkers position plus coin state, and find that their ratio is dependent on θ, but saturates to a constant value, meaning that the walker may probe its coin parameter quite faithfully.

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Section: Evolution In Discrete-time Quantum Walkmentioning

confidence: 99%

Quantum walker as a probe for its coin parameter

2019

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“…By free, we mean that the particle is affected only by the constraining potential that forces it to stay on the surface. The rationale behind this approach is that quantum systems are inherently sensitive to the parameters of their Hamiltonians, which may be exploited to precisely estimate the values of those parameters by performing suitable measurements on them [23][24][25][26][27][28][29][30][31][32]. This idea has been recently exploited to develop a new approach to probe macroscopic systems, based on the quantification and optimisation of the information that can be extracted by an interacting quantum probe as opposed to a classical one.…”

Section: Sensing the Curvature By A Free Particlementioning

confidence: 99%

Quantum Sensing of Curvature

2019

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We address the problem of sensing the curvature of a manifold by performing measurements on a particle constrained to the manifold itself. In particular, we consider situations where the dynamics of the particle is quantum mechanical and the manifold is a surface embedded in the three-dimensional Euclidean space. We exploit ideas and tools from quantum estimation theory to quantify the amount of information encoded into a state of the particle, and to seek for optimal probing schemes, able to actually extract this information. Explicit results are found for a free probing particle and in the presence of a magnetic field. We also address precision achievable by position measurement, and show that it provides a nearly optimal detection scheme, at least to estimate the radius of a sphere or a cylinder.

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“…An important problem in network theory is the extraction of information about the network when only a small subset of its constituents can be accessed. This has also been considered in the quantum case, and it has been shown that, provided one has suitable prior knowledge of the network, it is possible to determine several of its properties indirectly using a probe system, such as the network state 25 , temperature 26 , 27 , and coupling strengths between nodes 28 , 29 . In particular, in the case of full access, the structure of the network can in principle be determined exactly 9 , 30 .…”

Section: Introductionmentioning

confidence: 99%

Local probe for connectivity and coupling strength in quantum complex networks

Nokkala

Maniscalco

Piilo

2018

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We develop a local probe to estimate the connectivity of complex quantum networks. Our results show how global properties of different classes of complex networks can be estimated – in quantitative manner with high accuracy – by coupling a probe to a single node of the network. Here, our interest is focused on probing the connectivity, i.e. the degree sequence, and the value of the coupling constant within the complex network. The scheme combines results on classical graph theory with the ability to develop quantum probes for networks of quantum harmonic oscillators. Whilst our results are proof-of-principle type, within the emerging field of quantum complex networks they may have potential applications for example to the efficient transfer of quantum information or energy or possibly to shed light on the connection between network structure and dynamics.

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Characterization of qubit chains by Feynman probes

Cited by 46 publications

References 59 publications

Quantum walker as a probe for its coin parameter

Quantum walker as a probe for its coin parameter

Quantum Sensing of Curvature

Local probe for connectivity and coupling strength in quantum complex networks

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