Heralded noiseless amplification and entanglement distillation

以下のように8月9日（水）午後2時より大阪大学産業科学研究所 管理棟講堂にて、オーストラリア Griffith 大学のPryde教授の講演会を開催いたします。

Pryde教授は、量子光学・量子情報分野で著名な研究者で、最近もNature系雑誌等に多くの論文を発表されています。

光子のもつれあいを用いた量子情報処理（量子計算・量子通信・量子測定など）やそれによる古典系の量子制御に取り組まれておられます。また、固体中にドープされたイオンを用いたアンサンブル量子ビットの研究なども手がけておられます。

本講演では、大学院生や分野外の方の参加を念頭に、グリフィス大学における量子情報処処理の研究の一般的な紹介から、量子状態の伝令付き増幅という最先端の研究までご講演頂く予定です。

なお、本講演は大阪大学産業科学研究所にて開催されます。もし、大阪出張等、機会がありますようでしたら、ぜひともご参加ください。

After a general introduction about the work pursued in the Quantum Optics and Information Laboratory at Griffith University, I will discuss experiments on heralded noiseless amplification of quantum states.

Signal amplification is ubiquitous in the control of physical systems, and the ultimate performance limit of amplifiers is set by quantum physics. Deterministically increasing the amplitude of an unknown quantum optical field, or any harmonic oscillator state, must introduce noise. We introduce, and experimentally demonstrate, a *heralded* noiseless linear amplifier for quantum states of a single mode of the optical field, and use it for distillation of field-mode entanglement. This simple but powerful circuit enables practical devices for enhancing quantum technologies, and promises applications in quantum metrology and communications.

Another particularly interesting task is the amplification of a photonic qubit subjected to loss. Photonic qubits are the most common states for encoding optical quantum information for long-distance transmission, but loss is problematic. Amplifying optical qubit states has direct and major application in long-range quantum communications — through quantum repeaters and device-independent QKD protocols — and in other quantum technologies and fundamental investigations of quantum physics. We demonstrate a heralded noiseless amplifier for photonic qubit states. In particular, our qubit amplifier reduces the loss in a qubit channel, in a heralded fashion — successful operation is flagged by an independent signal, and does not rely on postselection of the output signal. We demonstrate a five-times increase in input-output state fidelity when using such an amplifier in a highly lossy photonic qubit channel, compared to just the channel alone.