Quantum 8, 1519 (2024). https://doi.org/10.22331/q-2024-11-07-1519 Quantum kernel methods are a proposal for achieving quantum computational advantage in machine learning. They are based on a hybrid classical-quantum computation where a function called the quantum kernel is […]
Quantum 8, 1518 (2024). https://doi.org/10.22331/q-2024-11-07-1518 One of quantum theory’s salient features is its apparent indeterminism, i.e. measurement outcomes are typically probabilistic. We formally define and address whether this uncertainty is unavoidable or whether post-quantum theories […]
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 […]
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