Partial measurements and the realization of quantum-mechanical counterfactuals

Abstract

We propose partial measurements as a conceptual tool to understand how to operate with counterfactual claims in quantum physics. Indeed, unlike standard von Neumann measurements, partial measurements can be reversed probabilistically. We first analyze the consequences of this rather unusual feature for the principle of superposition, for the complementarity principle, and for the issue of hidden variables. Then we move on to exploring non-local contexts, by reformulating the EPR paradox, the quantum teleportation experiment, and the entanglement-swapping protocol for the situation in which one uses partial measurements followed by their stochastic reversal. This leads to a number of counter-intuitive results, which are shown to be resolved if we give up the the idea of attributing reality to the wavefunction of a single quantum system.

22 pages, 3 figures

References in corpus (6)

• Undoing a weak quantum measurement of a solid-state qubit
• High-fidelity entanglement swapping with fully independent sources
• Signatures of quantum behavior in single-qubit weak measurements
• Interaction-free measurements with superconducting qubits
• Estimating the expectation values of spin 1/2 observables with finite resources
• Realism and single-quanta nonlocality

Cited by in corpus (4)

• Quantum simulation of parity-time symmetry breaking with a superconducting quantum processor
• Enhancing robustness of multiparty quantum correlations using weak measurement
• Coherent interaction-free detection of microwave pulses with a superconducting circuit
• Coherent interaction-free detection of noise