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Jakub J. Borkała

Publications and source records attributed to Jakub J. Borkała.

3 recordsLinked to original sources

Self-testing of any pure entangled state with minimal number of measurements and optimal randomness certification in one-sided device-independent scenario

Certification of quantum systems and their properties has become a field of intensive studies. Here, taking advantage of the one-sided device-independent scenario (known also as quantum steering scenario), we propose a self-testing scheme for all bipartite entangled states using a single family of steering inequalities with the minimal number of two measurements per party. Building on this scheme we then show how to certify all rank-one extremal measurements, including non-projective $d^2$-outcome measurements, which in turn can be used for certification of the maximal amount of randomness from every entangled bipartite state of local dimension $d$, that is, $2\log_2d$ bits. Finally, in a particular case of $d=3$, we extend our self-testing results to the fully device-independent setting.

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Semi-device-independent self-testing of unsharp measurements

Unsharp quantum measurements provide a resource in scenarios where one faces the trade-off between information gain and disturbance. In this work we introduce a prepare-transform-measure scenario in which two-outcome unsharp measurements outperform their sharp counterparts, as well as any stochastic strategy involving dichotomic projective measurements. Based on that, we propose a scheme for semi-device-independent self-testing of unsharp measurements and show that all two-outcome qubit measurements can be characterized in a robust way. Along with the main result, in this work we introduce a method, based on semidefinite programming, for bounding quantum correlations in scenarios with sequential measurements of length two. This method can also be applied to refine security analysis of the semi-device-independent one-way quantum key distribution. We also present new information gain-disturbance relation for pairs of dichotomic measurements.

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Connections Between Mutually Unbiased Bases and Quantum Random Access Codes

We present a new quantum communication complexity protocol, the promise--Quantum Random Access Code, which allows us to introduce a new measure of unbiasedness for bases of Hilbert spaces. The proposed measure possesses a clear operational meaning and can be used to investigate whether a specific number of mutually unbiased bases exist in a given dimension by employing Semi--Definite Programming techniques.

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