FIRST Project on Quantum Information Processing news letter = 内閣府最先端研究開発支援プログラム「量子情報処理プロジェクト」ニュースレター

Hai‐Zhi Song

最先端研究開発支援プログラム「量子情報処理プロジェクト」, 国立情報学研究所量子情報国際研究センター, 革新的研究開発推進プログラム「量子人工脳を量子ネットワークでつなぐ高度知識社会基盤の実現」

Seth Lloyd

Recent models of the black-hole final state suggest that quantum information can escape from a black hole by a process akin to teleportation. These models rely on a controversial process called final-state projection. This Letter discusses the self-consistency of the final-state projection hypothesis and investigates escape from black holes for arbitrary final states and for generic interactions between matter and Hawking radiation. Quantum information escapes with fidelity approximately = (8/3pi)2: only half a bit of quantum information is lost on average, independent of the number of bits that escape from the hole.

Chaohan Cui, Kaushik Parasuram Seshadreesan, Saikat Guha +1 more

In this Letter, we propose a new approach to process high-dimensional quantum information encoded in a photon frequency domain. In contrast to previous approaches based on nonlinear optical processes, no active control of photon energy is required. Arbitrary unitary transformation and projection measurement can be realized with passive photonic circuits and time-resolving detection. A systematic circuit design for a quantum frequency comb with arbitrary size has been given. The criteria to verify quantum frequency correlation has been derived. By considering the practical condition of the detector's finite response time, we show that high-fidelity operation can be readily realized with current device performance. This work will pave the way towards scalable and high-fidelity quantum information processing based on high-dimensional frequency encoding.