Quantum 9, 1662 (2025). https://doi.org/10.22331/q-2025-03-14-1662 The Bell theorem is explored in terms of a trade-off relation between underlying assumptions within the hidden variable model framework. In this paper, recognizing the incorporation of hidden variables as […]
Quantum 9, 1661 (2025). https://doi.org/10.22331/q-2025-03-12-1661 In the NISQ era, where quantum information processing is hindered by the decoherence and dissipation of elementary quantum systems, developing new protocols to extend the lifetime of quantum states is […]
Quantum 9, 1660 (2025). https://doi.org/10.22331/q-2025-03-12-1660 Quantum reinforcement learning (QRL) is a promising paradigm for near-term quantum devices. While existing QRL methods have shown success in discrete action spaces, extending these techniques to continuous domains is […]
Quantum 9, 1659 (2025). https://doi.org/10.22331/q-2025-03-12-1659 This paper presents novel methods for optimizing multi-controlled quantum gates, which naturally arise in high-level quantum programming. Our primary approach involves rewriting $U(2)$ gates as $SU(2)$ gates, utilizing one auxiliary […]
Quantum 9, 1658 (2025). https://doi.org/10.22331/q-2025-03-10-1658 Parametrized quantum circuits (PQC) are quantum circuits which consist of both fixed and parametrized gates. In recent approaches to quantum machine learning (QML), PQCs are essentially ubiquitous and play the […]
Quantum 9, 1657 (2025). https://doi.org/10.22331/q-2025-03-10-1657 Computing key rates in quantum key distribution (QKD) numerically is essential to unlock more powerful protocols, that use more sophisticated measurement bases or quantum systems of higher dimension. It is […]
Quantum 9, 1656 (2025). https://doi.org/10.22331/q-2025-03-06-1656 We study the dynamics of an open quantum system linearly coupled to a bosonic reservoir. We show that, in the ultrastrong coupling limit, the system undergoes a nonselective measurement and […]
Quantum 9, 1655 (2025). https://doi.org/10.22331/q-2025-03-06-1655 The estimation of many-qubit observables is an essential task of quantum information processing. The generally applicable approach is to decompose the observables into weighted sums of multi-qubit Pauli strings, i.e., […]
Quantum 9, 1654 (2025). https://doi.org/10.22331/q-2025-03-06-1654 Device-independent (DI) quantum cryptography aims at providing secure cryptography with minimal trust in, or characterisation of, the underlying quantum devices. A key step in DI protocols is randomness extraction (or […]
Quantum 9, 1653 (2025). https://doi.org/10.22331/q-2025-03-05-1653 We consider an infinite-range interacting quantum spin-1/2 model, undergoing periodic kicking and dissipatively coupled with an environment. In the thermodynamic limit, it is described by classical mean-field equations that can […]
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