Multi-mode optical quantum memory for quantum processing and communication

S. A. Moiseev, M. M. Minnegaliev

Sender authentication is an important requirement for secure quantum communication networks. We propose programmable photon-echo quantum memory processing of a multi-time-bin photonic qudit for implementing a quantum-hash-based verification protocol. In this approach, using QM, sender (Alice) generates a quantum hash state by transforming a single stored photonic wave packet into the programmable photonic qudit. Bob's memory coherently maps the received time-bin photonic qudit into a single output mode according to phase encoding. Our scheme relies on a time-resolved coherent detection method introduced here, in which the coherent responses from individual time-bins are sequentially accumulated within Bob's spin coherence prior to the final sender verification. The key advantage of this coherent detection for quantum hashing is shown, and its potential applications are also discussed. The performed analysis demonstrates that experimentally verified parameters of contemporary optical quantum memories enable a proof of principle realization of the proposed architecture. These results reveal an additional role for quantum memories, serving not only as synchronization and repeater resources for long-distance quantum communication, but also as active elements for quantum hashing in conventional quantum key distribution systems.

Alexander I. Lvovsky, Barry C. Sanders, Wolfgang Tittel

Xiong, YanJuan

The development of the quantum computer challenges the security of classical communication. This is due to the security of classical encryption being based on the computational complexity of an algorithm, for example, the difficulty of factoring a number into its prime product. Quantum communication uses quantum mechanics to manipulate quantum states and exchange information between two locations. Quantum communication has proven to be unconditionally secure. However, the fact that the maximum transmission distance is largely limited by attenuation in the distribution link remains one of the biggest challenges for practical quantum communication. Quantum repeaters can greatly extend this communication transmission distance. To realize quantum repeaters, one requires quantum memories, entanglement swapping operations, and photon pair-sources. In addition, quantum repeaters greatly benefit - in terms of the achievable entanglement distribution rate - if they can incorporate some form of multiplexing. Multiplexing is possible in any of the available photonic modes, which for transmission in single-mode fibers amounts to polarization, spectral, and temporal modes. The polarization degree of freedom is undesirable because it only has two orthogonal modes. The choice of the spectral or temporal modes for multiplexing then depends on what is most compatible with other components in the setup, particularly the quantum memory, which is the most demanding component. Based on prior demonstrations in the lab of spectral multiplexing in rare-earth ion doped crystals, the purpose of my project has been to build a spectrally multi-mode photon pair-source. Our implementation of the spectrally multi-mode photon pair sources relies on a nonlinear optics process that involves the interaction of strong light and a non-linear crystal. To achieve the spectral selection of specific modes, the non-linear crystal is combined with a suitable cavity.

Jesse L Everett

Spectrotemporal encoding of optical quantum information is emerging as a powerful tool in quantum information technology. Processing of spectrotemporal information has recently been demonstrated in multi-mode quantum memories, based on extensions to memory protocols. We simulate one such process, the fractional Fourier transform, in a system based on a dual quantum memory composed of successive gradient echo memory and electromagnetically-induced transparency operations. We demonstrate the potential of electromagnetically-induced transparency systems for spectrotemporal processing.

K. F. Reim, Joshua Nunn, Virginia O. Lorenz +5 more

Byoung Seung HAM