Schrodinger's Cat in a Hot Trap

James D. Stein

Martijn Boerkamp

Superpositions of quantum states known as Schrödinger cat states can be created in “hot” environments with temperatures up to 1.8 K, according to researchers in Austria and Spain.

Octavio Castaños, Shahen Hacyan, Ramón López–Peña +1 more

The time-dependent Schrödinger equation of an ion moving in an asymmetric Penning trap is solved. Properties of the evolution of squeezed and Schrödinger cat states in the trap are studied. Analytic expressions for the energy expectation values, dispersions and correlations of the position and momentum operators of different macroscopic states, solutions of the time-dependent Schrödinger equation of the trap, are obtained. The probability densities in coordinate and momentum representations are also given. As an example, the behaviour of Schrödinger cat states of a proton moving in the trap is described numerically.

Philip Ball

Peter John Bussey

Ian Yang, Thomas E. G. Agrenius, Vasilisa Usova +2 more

The observation of quantum phenomena often necessitates sufficiently pure states, a requirement that can be challenging to achieve. In this study, our goal is to prepare a nonclassical state originating from a mixed state, using dynamics that preserve the initial low purity of the state. We generate a quantum superposition of displaced thermal states within a microwave cavity using only unitary interactions with a transmon qubit. We measure the Wigner functions of these "hot" Schrödinger cat states for an initial purity as low as 0.06. This corresponds to a cavity mode temperature of up to 1.8 kelvin, 60 times hotter than the cavity's physical environment. Our realization of highly mixed quantum superposition states could be implemented with other continuous-variable systems, e.g., nanomechanical oscillators, for which ground-state cooling remains challenging.