Quantum 7, 890 (2023). https://doi.org/10.22331/q-2023-01-03-890 We show that $Omega(rd/epsilon)$ copies of an unknown rank-$r$, dimension-$d$ quantum mixed state are necessary in order to learn a classical description with $1 – epsilon$ fidelity. This improves upon […]
Quantum 7, 889 (2023). https://doi.org/10.22331/q-2023-01-03-889 Measuring the expectation value of the molecular electronic Hamiltonian is one of the challenging parts of the variational quantum eigensolver. A widely used strategy is to express the Hamiltonian as […]
Quantum 7, 888 (2023). https://doi.org/10.22331/q-2023-01-03-888 Recent advances in laser interactions with coherent free electrons have enabled to shape the electron’s quantum state. Each electron becomes a superposition of energy levels on an infinite quantized ladder, […]
Quantum 6, 887 (2022). https://doi.org/10.22331/q-2022-12-29-887 Spin squeezing inequalities (SSI) represent a major tool to probe quantum entanglement among a collection of few-level atoms, and are based on collective spin measurements and their fluctuations. Yet, for […]
Quantum 6, 886 (2022). https://doi.org/10.22331/q-2022-12-29-886 We study the emergence over time of a universal, uniform distribution of quantum states supported on a finite subsystem, induced by projectively measuring the rest of the system. Dubbed $textit{deep […]
Quantum 6, 885 (2022). https://doi.org/10.22331/q-2022-12-29-885 We study the quantum synchronization of a single spin driven by an external semiclassical signal for spin numbers larger than $S = 1$, the smallest system to host a quantum […]
Quantum 6, 884 (2022). https://doi.org/10.22331/q-2022-12-22-884 Quantum speed limits (QSLs) identify fundamental time scales of physical processes by providing lower bounds on the rate of change of a quantum state or the expectation value of an […]
Quantum 6, 883 (2022). https://doi.org/10.22331/q-2022-12-22-883 Equivalent approaches to determine eigenfrequencies of the Liouvillians of open quantum systems are discussed using the solution of the Heisenberg-Langevin equations and the corresponding equations for operator moments. A simple […]
Quantum 6, 882 (2022). https://doi.org/10.22331/q-2022-12-22-882 This paper is concerned with complexity theoretic aspects of a general formulation of quantum game theory that models strategic interactions among rational agents that process and exchange quantum information. In […]
Quantum 6, 881 (2022). https://doi.org/10.22331/q-2022-12-22-881 Quantum machine learning techniques have been proposed as a way to potentially enhance performance in machine learning applications. In this paper, we introduce two new quantum methods for neural networks. […]
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