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Spooky Work at a Distance: an Interaction-Free Quantum Measurement-Driven Engine

Elouard, C.Waegell, M.Huard, B.Jordan, A.N. Department of Physics and Astronomy,
University of Rochester,

Institute for Quantum studies,
Chapman University,
Orange, CA, USA

Laboratoire de Physique,
Ecole Normale Sup ́erieure de Lyon,
2019 Physics

Recent progress in the science of quantum measurement has focused on the energy associated with the wavefunction collapse process. Energy may be stochastically transferred from the measurement probe to the system being measured, such that a highly efficient quantum measurement powered engine can be realized with cyclic feedback. Here we show that this work extraction can be done in a nonlocal way using interaction free measurements, despite a local interaction Hamiltonian. By putting an Elitzur-Vaidman bomb in one arm of a tuned Mach-Zehnder interferometer, the detection of a photon in the dark port of the interferometer indicates the bombs presence without blowing it up.

Treating the bomb quantum mechanically, the bombs ground state exists in superposition of inside and outside the interferometer arm. If the optical dark port fires, the bombs wavefunc- tion must collapse inside the interferometer arm, which raises the bombs energy. The energy can then be extracted in the engine cycle. Crucially, the wavefunction collapse of the bomb inside the interferometer arm indicates the photon could not have taken the path the bomb was localized in, otherwise it would have absorbed the photon and exploded.

Therefore, the work done on the bomb by the photon is seemingly nonlocal. We complement this discussion by calculating the anomalous measurable energy gain when postselecting realizations where the dark port fires. Regardless of interpretation, this interaction free quantum measurement engine is able to lift the most sensitive bomb without setting it off.

The article was published in: arXiv preprint arXiv:1904.09289

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This work was supported (in part) by the Fetzer Franklin Fund of the John E. Fetzer Memorial Trust.