Quantum 8, 1517 (2024). https://doi.org/10.22331/q-2024-11-07-1517 A Dicke state and its decohered state are invariant for permutation. However, when another qubits state to each of them is attached, the whole state is not invariant for permutation, […]
Quantum 8, 1516 (2024). https://doi.org/10.22331/q-2024-11-07-1516 Quantum computers are rapidly becoming more capable, with dramatic increases in both qubit count [1] and quality [2]. Among different hardware approaches, trapped-ion quantum processors are a leading technology for […]
Quantum 8, 1515 (2024). https://doi.org/10.22331/q-2024-11-07-1515 A prepare-and-measure scenario is naturally described by a communication matrix that collects all conditional outcome probabilities of the scenario into a row-stochastic matrix. The set of all possible communication matrices […]
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 […]
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