Universal Continuous Variable Quantum Computation Without Cooling

Abstract: One of the limitations to the quantum computing capability of a continuous-variable system is determined by our ability to cool it to the ground state, because pure logical states, in which we accurately encode quantum information, are conventionally pure physical states that are constructed from the ground state. In this work, we present an alternative quantum computing formalism that encodes logical quantum information in mixed physical states. We introduce a class of mixed-state protocols that are based on a parity encoding, and propose an implementation of the universal logic gates by using realistic hybrid interactions. When comparing with the conventional pure-state protocols, our formalism could relax the necessity of, and hence the systemic requirements of cooling. Additionally, the mixed-state protocols are inherently resilient to a wider class of noise processes, and reduce the fundamental energy consumption in initialisation. Our work broadens the candidates of continuous-variable quantum computers.