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Physics

Undoing a quantum measurement

Christoph Bruder, Daniel Loss

Published Nov 10, 2008• 3 citations
Publisher

Abstract

Quantum measurements are conventionally thought of as irretrievably “collapsing” a wave function to the observed state. However, experiments with superconducting qubits show that the partial collapse resulting from a weak continuous measurement can be restored.
DOI
10.1103/physics.1.34

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We describe an experiment using superconducting transmon qubits that demonstrates wavefunction collapse consistent with Orchestrated Objective Reduction (Orch-OR) - the theory of consciousness proposed by Sir Roger Penrose and Stuart Hameroff. The experiment performs a partial measurement on a qubit. It uses the result of that measurement to move an estimated 10e-12 kg of mass in one of two locations separated by approximately 1 mm. In standard quantum mechanics, the partial measurement leaves the system in an improper mixture, a state that appears probabilistic but retains quantum coherence. This is mathematically indistinguishable from a proper mixture, where the state has genuinely collapsed. According to Penrose's theory, improper mixtures can lead to gravitationally induced collapse. Results of our experiment show a change in the circuit evolution that is consistent with wavefunction collapse driven by such an improper mixture. The experiment is performed on an IBM Eagle 127-qubit processor using IBM's programming framework Qiskit.