Quantum 9, 1726 (2025). https://doi.org/10.22331/q-2025-05-05-1726 We present an iterative generalisation of the quantum subspace expansion algorithm used with a Krylov basis. The iterative construction connects a sequence of subspaces via their lowest energy states. Diagonalising […]
Quantum 9, 1725 (2025). https://doi.org/10.22331/q-2025-05-05-1725 We study the estimation of relative entropy $D(rho|sigma)$ when $sigma$ is known. We show that the Cramér-Rao type bound equals the relative varentropy. Our estimator attains the Cramér-Rao type bound […]
Quantum 9, 1724 (2025). https://doi.org/10.22331/q-2025-05-05-1724 Current noisy quantum computers have multiple types of errors, which can occur in the state preparation, measurement/readout, and gate operation, as well as intrinsic decoherence and relaxation. Partly motivated by […]
Quantum 9, 1723 (2025). https://doi.org/10.22331/q-2025-05-05-1723 In this work, we introduce a method to construct fault-tolerant $textit{measurement-based quantum computation}$ (MBQC) architectures and numerically estimate their performance over various types of networks. A possible application of such […]
Quantum 9, 1722 (2025). https://doi.org/10.22331/q-2025-04-24-1722 One significant advantage of superconducting processors is their extensive design flexibility, which encompasses various types of qubits and interactions. Given the large number of tunable parameters of a processor, the […]
Quantum 9, 1721 (2025). https://doi.org/10.22331/q-2025-04-24-1721 Motivated by the expectation that relativistic symmetries might acquire quantum features in Quantum Gravity, we take the first steps towards a theory of ”Doubly” Quantum Mechanics, a modification of Quantum […]
Quantum 9, 1720 (2025). https://doi.org/10.22331/q-2025-04-24-1720 This paper introduces the foliage partition, an easy-to-compute LC-invariant for graph states, of computational complexity $mathcal{O}(n^3)$ in the number of qubits. Inspired by the foliage of a graph, our invariant […]
Quantum 9, 1719 (2025). https://doi.org/10.22331/q-2025-04-24-1719 While in relativity theory space evolves over time into a single entity known as spacetime, quantum theory lacks a standard notion of how to encapsulate the dynamical evolution of a […]
Quantum 9, 1718 (2025). https://doi.org/10.22331/q-2025-04-18-1718 We work out the general theory of one-parameter families of partial entanglement properties and the resulting entanglement depth-like quantities. Special cases of these are the depth of partitionability, the depth […]
Quantum 9, 1717 (2025). https://doi.org/10.22331/q-2025-04-18-1717 In unitary property testing a quantum algorithm, also known as a tester, is given query access to a black-box unitary and has to decide whether it satisfies some property. We […]
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