Role of the Schrödinger Cat State in Quantum Information

David Vitali

Shi-Wen He, Xuanxuan Xin, Feng‐Yang Zhang +1 more

The hybrid system between the transmon and the magnon plays an important role in quantum information science. Additionally, the cat states of the magnon are a valuable quantum resource and represent macroscopic quantum superpositions of large numbers of spins. In this paper, we propose an approach to generate magnonic Schr\"odinger cat states (SCSs) in a hybrid ferromagnet-superconductor system. Moreover, high-fidelity magnonic SCSs can be generated when the dissipation of the system is considered. The coherent amplitude and the fidelities of the cat states can be adjusted by controlling the parameters of the system.

Miriam Resch, Ciprian Padurariu, Björn Kubala +1 more

Schrödinger cat states play an important role for applications in continuous variable quantum information technologies. As macroscopic superpositions, they are inherently protected against certain types of noise making cat qubits a promising candidate for quantum computing. It has been shown recently that cat states occur naturally in driven Kerr parametric oscillators as degenerate ground states with even and odd parity that are adiabatically connected to the respective lowest two Fock states by switching off the drive. To perform operations with several cat qubits, one crucial task is to create entanglement between them. Here, we demonstrate efficient transformations of multimode cat states through adiabatic and diabatic switching between Kerr-type Hamiltonians with degenerate ground-state manifolds. These transformations can be used to directly initialize the cats as entangled Bell states in contrast to initializing them from entangled Fock states.

M. Kira, S. W. Koch, Ryan P. Smith +2 more

Phil Maguire, Rebecca Maguire

We reopen Erwin Schrodinger's thought experiment involving a cat in an informationally impenetrable box. A common view is that the cat enters a superposition of alive/dead because of a lack of observation, leading to uncertainty about the state of the cat. We, on the other hand, argue that the cat only enters a superposition if everything about the cat is known prior to the box being closed. The superposition results from a lack of uncertainty inside the box. Rather than interpreting this state of affairs as a live and dead cat interacting with each other, we suggest that the more natural interpretation is that of an inability to precisely position events within spacetime due to the lack of uncertainty. We clarify how stable measurement depends on a diversified portfolio of statistical uncertainty, and how the lack of such uncertainty in Schrodinger's box precludes stabilization.

Paul G. Kwiat