Quantum 8, 1514 (2024). https://doi.org/10.22331/q-2024-10-30-1514 Causal nonseparability is the property underlying quantum processes incompatible with a definite causal order. So far it has remained a central open question as to whether any process with a […]
Quantum 8, 1513 (2024). https://doi.org/10.22331/q-2024-10-29-1513 We propose a protocol to realize quantum simulation and computation in spin systems with long-range interactions. Our approach relies on the local addressing of single spins with external fields parametrized […]
Quantum 8, 1512 (2024). https://doi.org/10.22331/q-2024-10-29-1512 Multivariable Quantum Signal Processing (M-QSP) [1] is expected to provide an efficient means to handle polynomial transformations of multiple variables simultaneously. However, we identified several inconsistencies in the main theorem, […]
Quantum 8, 1511 (2024). https://doi.org/10.22331/q-2024-10-28-1511 Real quantum computers will be subject to complicated, qubit-dependent noise, instead of simple noise such as depolarizing noise with the same strength for all qubits. We can do quantum error […]
Quantum 8, 1510 (2024). https://doi.org/10.22331/q-2024-10-24-1510 We present an explicit quantum circuit that prepares an arbitrary $U(1)$-eigenstate on a quantum computer, including the exact eigenstates of the spin-$1/2 XXZ$ quantum spin chain with either open or […]
Quantum 8, 1509 (2024). https://doi.org/10.22331/q-2024-10-24-1509 We investigate the limitations of quantum computers for solving nonlinear dynamical systems. In particular, we tighten the worst-case bounds of the quantum Carleman linearisation (QCL) algorithm [Liu et al., PNAS […]
Quantum 8, 1508 (2024). https://doi.org/10.22331/q-2024-10-23-1508 The formalism of quantum theory over discrete systems is extended in two significant ways. First, quantum evolutions are generalized to act over entire network configurations, so that nodes may find […]
Quantum 8, 1507 (2024). https://doi.org/10.22331/q-2024-10-23-1507 Oblivious linear evaluation is a generalization of oblivious transfer, whereby two distrustful parties obliviously compute a linear function, $f (x) = ax + b$, i.e., each one provides their inputs […]
Quantum 8, 1506 (2024). https://doi.org/10.22331/q-2024-10-23-1506 In classical computing, error-correcting codes are well established and are ubiquitous both in theory and practical applications. For quantum computing, error-correction is essential as well, but harder to realize, coming […]
Quantum 8, 1505 (2024). https://doi.org/10.22331/q-2024-10-23-1505 We propose a simple, robust protocol to prepare a low-energy state of an arbitrary Hamiltonian on a quantum computer or programmable quantum simulator. The protocol is inspired by the adiabatic […]
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