Measurement-induced macroscopic superposition states in cavity optomechanics

Thursday 06 Oct 16
by Sepehr Ahmadi


Ulrich Busk Hoff
Senior Adviser
DTU Physics
+45 29 80 41 55
Researchers from the QPIT section at DTU Physics have conceived a new optomechanical protocol for generating Schrödinger cat-like states of a mechanical oscillator, adding renewed hope for the long-standing goal of observing quantum phenomena at macroscopic scales.

Ulrich B. Hoff, Johann Kollath-Bönig, Jonas S. Neergaard-Nielsen, & Ulrik L. Andersen

Physical Review Letters, 117, 143601, (2016). DOI:

Publication date (online): September 28, 2016

Schrödinger’s cat is the quintessential embodiment of the manifestly non-classical properties of quantum mechanics, simultaneously occupying two macroscopically distinct states – dead and alive. So far, such coherent state superpositions have only been observed for isolated microscopic quantum systems. An intriguing question is whether also macroscopic objects can be prepared in quantum superpositions of being here and there?

A vast number of proposals for optomechanical generation of cat states exist in the literature. But they all rely on an extremely strong non-Gaussian interaction between light and mechanics, and are thus of limited practical feasibility even for state-of-the-art optomechanical systems. In their recent paper, the authors propose a squeezed-light enhanced cavity optomechanical protocol for preparing a macroscopic mechanical trampoline resonator consisting of 1012 atoms in a coherent superpostion of two distinct oscillation phases. Employing squeezed light, an optical Schrödinger cat state is initially prepared, and by a subsequent pulsed quantum non-demolition interaction that state is transferred onto the mechanical oscillator. That leaves the mechanics in a state where the trampoline is simultaneously depressed downwards and protruding upwards, realising a macroscopic quantum superposition state.

Most importantly, the protocol is consistent with existing optomechanical systems and already demonstrated optical resources. Thus, the authors proposal offers an experimentally feasible route towards the long-standing goal of interrogating quantum phenomena at the macroscopic scale.

Wigner function representation of a macroscopic mechanical superposition state.