Interaction-free measurements by quantum Zeno stabilization of ultracold atoms

Abstract

Quantum mechanics predicts that our physical reality is influenced by events that can potentially happen but factually do not occur. Interaction-free measurements (IFMs) exploit this counterintuitive influence to detect the presence of an object without requiring any interaction with it. Here we propose and realize an IFM concept based on an unstable many-particle system. In our experiments, we employ an ultracold gas in an unstable spin configuration, which can undergo a rapid decay. The object—realized by a laser beam—prevents this decay because of the indirect quantum Zeno effect and thus, its presence can be detected without interacting with a single atom. Contrary to existing proposals, our IFM does not require single-particle sources and is only weakly affected by losses and decoherence. We demonstrate confidence levels of 90%, well beyond previous optical experiments.

Effective electrostatic attraction between electrons due to quantum interference

“…Quantum interference may result in many nonintuitive phenomena such as interferometry with massive particles [1][2][3], quantum delayed choice experiments [4][5][6], quantum erasers [7][8][9][10], "interaction-free" measurements [11][12][13] or the Hong-Ou-Mandel effect [14][15][16]. Here we discuss an example of the counter-intuitive characteristics of quantum interference inspired by a recent work by Aharonov et al [17] and following the discussions of an earlier paper from our group [18].…”

Observation of quantum Zeno effect in a superconducting flux qubit

“…This is called the anti-Zeno effect. These phenomena were first observed in a radio frequency (RF) transition between two 9 Be + ground state hyperfine levels [15], then nuclear magnetic resonance (NMR) [16] and atomic systems [17][18][19][20][21][22][23][24][25].…”

Interaction-free ghost-imaging of structured objects

“…Enhancements of the original method [6] involve the quantum Zeno effect [7,8], as well as more elaborate schemes based on induced coherence without induced emission [9]. Similar interaction-free measurements have also found many applications in quantum computation and communication [10,11], stabilizing ultracold atoms [12], orbital angular momentum spectrometry [13] and optical switching [14].…”