[3분논문] 제12회 - 양자 순간이동. 143 km 전송

황용섭의 3분논문 제12회입니다.

총시간은 5분 26초입니다.

재미있게 논문 보면서 들어보세요.

# 방송 바로 듣기

1. 12_3분논문_제12회.mp3

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# 논문표지

# 간단한 정보

글쓴이: Xiao-Song Ma, Thomas Herbst, Thomas Scheidl, Daqing Wang,

           Sebastian Kropatschek, William Naylor, Bernhard Wittmann, Alexandra Mech,

           Johannes Kofler, Elena Anisimova, Vadim Makarov, Thomas Jennewein, 

           Rupert Ursin & Anton Zeilinger

제목: Quantum teleportation over 143 kilometres using active feed-forward

학술지: Nature

발행년월: 2012년 9월

이어가기: http://dx.doi.org/10.1038/nature11472

# 용어

- quantum teleportation: 양자 순간이동. 양자정보단위(qubit)를 한 위치에서 다른 위치로 정확하게 전송하는 방법.

- quantum entanglement: 양자 얽힘. 양쪽의 양자상태가 서로에게 영향을 받는 상태. 양자 얽힘에 의하면 물리적으로 얽히도록 만든 양자쌍을 공간적으로 띄어놓아도 여전히 얽혀있다. 

# 발췌

1.

To achieve this, we combine advanced techniques involving a frequency-uncorrelated polarization-entangled photon pair source, ultra-low-noise single-photon detectors and entanglement-assisted clock synchronization.

2.

the experiment presented in this Letter achieves long-distance free-space teleportation of an independent quantum state, thus paving the way for satellite-based global quantum communication.

# 그림

Figure 1: Quantum teleportation between the Canary Islands La Palma and Tenerife over both quantum and classical 143-km free-space channels.

a, Experimental scheme. Alice and Charlie are situated in La Palma, and Bob in Tenerife. Charlie prepares the teleportation input photon 1 in |φ₁, using a heralded single-photon (HSP) source with a trigger photon 0 (photons are indicated by black numerals on red circles). An Einstein–Podolsky–Rosen (EPR)²³ source generates an entangled pair of photons 2 and 3 in the state |Ψ⁻₂₃. Alice then performs a Bell-state measurement (BSM) on photons 1 and 2, and projects them onto two of the four Bell states (|Ψ⁻₁₂/|Ψ⁺₁₂), and sends the result via the classical feed-forward channel to Bob. Photon 3 is sent via the free-space quantum channel to Bob, who applies a unitary transformation (identity operation or  phase shift) on photon 3 depending on the BSM result and thus turns its state |φ₃ into a replica of the initial quantum state |φ₁. b, Set-up. In La Palma, a frequency-uncorrelated polarization-entangled photon pair source generated photons 2 and 3 in BBO₁ (EPR/Alice) and a collinear photon pair source generated photons 0 and 1 in BBO₂ (HSP/Charlie). All single photons were coupled into single-mode fibres. For implementing the BSM, photons 1 and 2 interfered in a fibre beam splitter (FBS) followed by polarization-resolving single-photon detection (BSM/Alice). Photon 3 was guided to the transmitter telescope via a 100-m single-mode fibre and sent to Bob in Tenerife, where the unitary transformation was implemented using an electro-optical modulator (EOM) and photon 3’s polarization was measured. A real-time feed-forward operation was implemented by encoding the |Ψ⁺₁₂ BSM result in 1,064-nm laser pulses, which were then sent to Bob via the feed-forward channel. On Bob’s side, they were separated by a dichroic mirror (DM), detected with a photodetector (PD) and used to trigger the EOM to perform the required πphase shift operation. See main text for details.

# 결론

양자상태를 무려 143km라는 거리를 이동시켰다는 점은 매우 놀랍다. 한 달 전에 중국에서 한 비슷한 실험과 더불어 물리학 역사에 길이 남을 실험이라고 생각한다. 멋지다. 훌륭하다.

# 저자 인터뷰 (네이처 팟캐스트)

네이처에서 운영하는 팟캐스트 방송에서 교신저자인 Anton Zeilinger의 인터뷰했습니다. 듣고 싶은 분을 위해 그 부분을 편집하여 올려둡니다.

1. crop_nature-podcast--2012-09-06.mp3

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# 같이 읽을 논문

불과 한 달 전 네이처에 비슷한 내용으로 다른 연구단에서 발표한 논문이 있다. 함께 읽어보면 좋겠다.

글쓴이: Juan Yin, Ji-Gang Ren, He Lu, Yuan Cao, Hai-Lin Yong, Yu-Ping Wu,

           Chang Liu, Sheng-Kai Liao, Fei Zhou, Yan Jiang, Xin-Dong Cai, Ping Xu,

           Ge-Sheng Pan, Jian-Jun Jia, Yong-Mei Huang, Hao Yin, Jian-Yu Wang,

           Yu-Ao Chen, Cheng-Zhi Peng & Jian-Wei Pan

제목: Quantum teleportation and entanglement distribution over 100-kilometre free-space channels

학술지: Nature

발행년월: 2012년 8월

이어가기: http://dx.doi.org/10.1038/nature11332