Fidelity of dynamical maps

Tukiainen, Mikko; Lyyra, Henri; Sarbicki, Gniewomir; Maniscalco, Sabrina

doi:10.1103/physreva.95.052102

Cited by 8 publications

(24 citation statements)

References 49 publications

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“…In this section we address these issues by introducing an inequality between measures of "closeness" of the programming resources and the corresponding programmed observables. We note that similar analysis was recently made for programming of quantum channels in [16].…”

Section: Limitations On Quantum Programmingsupporting

confidence: 63%

Limitations on post-processing assisted quantum programming

Heinosaari¹,

Miyadera²,

Tukiainen³

2017

Quantum Inf Process

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A quantum multimeter is a programmable device that can implement measurements of different observables depending on the programming quantum state inserted into it. The advantage of this arrangement over a single purpose device is in its versatility: one can realize various measurements simply by changing the programming state. The classical manipulation of measurement output data is known as post-processing. In this work we study the post-processing assisted quantum programming, which is a protocol where quantum programming and classical post-processing are combined. We provide examples showing that these two processes combined can be more efficient than either of them used separately. Furthermore, we derive an inequality relating the programming resources to their corresponding programmed observables, thereby enabling us to study the limitations on post-processing assisted quantum programming.Comment: 17 pages, 2 figures. Final ver. 2: summary section added and some typos correcte

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Section: Limitations On Quantum Programmingsupporting

confidence: 63%

Limitations on post-processing assisted quantum programming

Heinosaari¹,

Miyadera²,

Tukiainen³

2017

Quantum Inf Process

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“…In short, we believe that the present study may trigger various further analytic as well as experimental researches with possible connection to spintronics and topological computations. We should mention here that experimentally, quantification of concurrence is possible using different protocols for both pure states 53,54 and mixed states 53 and it will be interesting if that can be pursued for our Floquet system and compared with our numerical results.…”

Section: Discussionmentioning

confidence: 99%

Photoinduced entanglement in a magnonic Floquet topological insulator

Kar

Basu

2018

Phys. Rev. B

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When irradiated via high frequency circularly polarized light, the stroboscopic dynamics in a Heisenberg spin system on a honeycomb lattice develops a next nearest neighbor (NNN) Dzyaloshinskii-Moriya (DM) type term 37 , making it a magnonic Floquet topological insulator. We investigate the entanglement generation and its evolution on such systems -particularly an irradiated ferromagnetic XXZ spin-1 2 model in a honeycomb lattice as the system parameters are optically tuned. In the high frequency limit, we compute the lowest quasi-energy state entanglement in terms of the concurrence between nearest neighbor (NN) and NNN pair of spins and witness the entanglement transitions occurring there. For the easy axis scenario, the unirradiated system forms a product state but entanglement grows between the NNN spin pairs beyond some cut-off DM strength. Contrarily in easy planar case, NN and NNN spins remain already entangled in the unirradiated limit. It then goes through an entanglement transition which causes decrease (increase) of the NN (NNN) concurrences down to zero (up to some higher value) at some critical finite DM interaction strength. For a high frequency of irradiation and a suitably chosen anisotropy parameter, we can vary the field strength to witness sudden death and revival of entanglement in the Floquet system. Both exact diagonalization and modified Lanczos techniques are used to obtain the results upto 24 site lattice. We also calculate the thermal entanglement and obtain estimates for the threshold temperatures below which non-zero concurrence can be expected in the system. arXiv:1806.02125v3 [cond-mat.str-el]

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“…In contrary to all known methods of probing the environment (up to our best knowledge), our method does not require any knowledge about the mechanism of interaction. For details, see [5].…”

Section: Discussionmentioning

confidence: 99%

Interaction Independent Quantum Probing

et al. 2017

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For an open quantum system we assume that we are able to set the system's environment temperature. We fix the time interval and let the system (further referred as the probing system) to evolve during this time in two different temperatures. We make a process tomography of the resulting dynamics (quantum channels ε1, ε2 related to the temperatures T1 and T2 respectively). We calculate then the values of α-fidelities for the pair of channels. We derive an inequality between the experimental data and the partition function of environment (hence the spectrum of the environment). If the inequality is not satisfied, it implies that our assumption about the spectrum of the environment is wrong. Notice that there is no dependence on the interaction terms neither on the Hamiltonian of the probing system. We show the power of this method in the following example. Consider a two-level atom passing the one-mode vacuum. We do not know the Hamiltonian of the atom (the probing system) neither the interaction mechanism. We would like to determine the frequency of the vacuum. We will show that wide range of frequencies are forbidden by the inequality.

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Fidelity of dynamical maps

Cited by 8 publications

References 49 publications

Limitations on post-processing assisted quantum programming

Limitations on post-processing assisted quantum programming

Photoinduced entanglement in a magnonic Floquet topological insulator

Interaction Independent Quantum Probing

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