Quantum optical coherence can survive photon losses using a continuous-variable quantum erasure-correcting code

Abstract

A fundamental requirement for enabling fault-tolerant quantum information processing is an efficient quantum error-correcting code that robustly protects the involved fragile quantum states from their environment1,2,3,4,5,6,7,8,9,10. Just as classical error-correcting codes are indispensible in today's information technologies, it is believed that quantum error-correcting code will play a similarly crucial role in tomorrow's quantum information systems. Here, we report on the experimental demonstration of a quantum erasure-correcting code that overcomes the devastating effect of photon losses. Our quantum code is based on linear optics, and it protects a four-mode entangled mesoscopic state of light against erasures. We investigate two approaches for circumventing in-line losses, and demonstrate that both approaches exhibit transmission fidelities beyond what is possible by classical means. Because in-line attenuation is generally the strongest limitation to quantum communication, such an erasure-correcting code provides a new tool for establishing quantum optical coherence over longer distances. The effect of loss on quantum states is one of the major hurdles in quantum communications. A quantum error-correcting code that overcomes erasure due to photon loss is experimentally demonstrated. The scheme uses linear optics and protects a four-mode entangled mesoscopic state of light.