Quantum 6, 665 (2022). https://doi.org/10.22331/q-2022-03-10-665 Multiparameter quantum estimation is made difficult by the following three obstacles. First, incompatibility among different physical quantities poses a limit on the attainable precision. Second, the ultimate precision is not […]
Quantum 6, 664 (2022). https://doi.org/10.22331/q-2022-03-03-664 This article proposes the first discrete-time implementation of Rydberg quantum walk in multi-dimensional spatial space that could ideally simulate different classes of topological insulators. Using distance-selective exchange-interaction between Rydberg excited […]
Quantum 6, 663 (2022). https://doi.org/10.22331/q-2022-03-01-663 The causal order of events need not be fixed: whether a bus arrives before or after another at a certain stop can depend on other variables – like traffic. Coherent […]
Quantum 6, 662 (2022). https://doi.org/10.22331/q-2022-03-01-662 For a classical channel, neither the Shannon ca-pa-city, nor the sum of conditional probabilities corresponding to the cases of successful transmission can be increased by the use of shared entanglement, […]
Quantum 6, 661 (2022). https://doi.org/10.22331/q-2022-02-24-661 We introduce the hemicubic codes, a family of quantum codes obtained by associating qubits with the $p$-faces of the $n$-cube (for $n>p$) and stabilizer constraints with faces of dimension $(ppm1)$. […]
Quantum 6, 660 (2022). https://doi.org/10.22331/q-2022-02-24-660 Many applications in quantum communication, sensing and computation need provably quantum non-Gaussian light. Recently such light, witnessed by a negative Wigner function, has been estimated using homodyne tomography from a […]
Quantum 6, 659 (2022). https://doi.org/10.22331/q-2022-02-21-659 Spekkens has introduced an $textit{epistemically restricted classical theory}$ of discrete systems, based on discrete phase space. The theory manifests a number of quantum-like properties but cannot fully imitate quantum theory […]
Quantum 6, 658 (2022). https://doi.org/10.22331/q-2022-02-21-658 We consider online strategies for discriminating between symmetric pure states with zero error when $n$ copies of the states are provided. Optimized online strategies involve local, possibly adaptive measurements on […]
Quantum 6, 657 (2022). https://doi.org/10.22331/q-2022-02-21-657 We propose a method to reliably and efficiently extract the fidelity of many-qubit quantum circuits composed of continuously parametrized two-qubit gates called matchgates. This method, which we call $textit{matchgate benchmarking}$, […]
Quantum 6, 656 (2022). https://doi.org/10.22331/q-2022-02-21-656 In this work, we characterize the amount of steerability present in quantum theory by connecting the maximal violation of a steering inequality to an inclusion problem of free spectrahedra. In […]
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