Distinguishability is a fundamental and operational measure generally connected to information applications. In quantum information theory, from the postulates of quantum mechanics it often has an intrinsic limitation, which then dictates and also characterises capabilities of related information tasks. In this work, we consider discrimination between bipartite two-qubit unitary transformations...

We theoretically investigate the spin dynamics of a heavy hole confined to an unstrained III-V semiconductor quantum dot and interacting with a narrowed nuclear-spin bath. We show that band hybridization leads to an exponential decay of hole-spin superpositions due to hyperfine-mediated nuclear pair flips, and that the accordant single-hole-spin decoherence time T2 can be tuned over many orders...

Heisenberg’s uncertainty principle is usually taken to express a limitation of operational possibilities imposed by quantum mechanics. Here we demonstrate that the full content of this principle also includes its positive role as a condition ensuring that mutually exclusive experimental options can be reconciled if an appropriate trade-off is accepted. The uncertainty principle is shown to appe...

The sign problem is the fundamental limitation to quantum Monte Carlo simulations of the statistical mechanics of interacting fermions. Determinant quantum Monte Carlo (DQMC) is one of the leading methods to study lattice fermions, such as the Hubbard Hamiltonian, which describe strongly correlated phenomena including magnetism, metal-insulator transitions, and possibly exotic superconductivity...

Periodically modulated nonlinear oscillators often display bistability of forced vibrations. This bistability can be used for new types of quantum measurements. They are based on switching between coexisting vibrational states. Since switching is accompanied by a large change of the amplitude and phase of forced vibrations, the measurements are highly sensitive. Quantum and classical noise play...

The problem of simulating sparse Hamiltonians on quantum computers is well-studied. The evolution of a sparse Hamiltonian H for time t can be simulated using O(‖Ht‖) operations, which is essentially optimal due to a no–fast-forwarding theorem. Here, we consider simulation of dense Hamiltonians. On the positive side, we show that some dense Hamiltonians can be simulated efficiently, such as thos...

Recent experiments on superconducting loops have demonstrated coherent superpositions between macroscopic quantum states. In the experiment of the superconducting persistent-current qubit, a dc SQUID measures the magnetic flux generated by the persistent currents of the macroscopic quantum states. Due to the inductive interaction between the qubit and the SQUID, the SQUID has various back effec...