Research press release


Nature Communications

Neuroscience: Humans can detect single photons



今回、Alipasha Vaziriたちは、量子光学技術を用いて、単一の光子を発生させる光源を設計し、3人の被験者による実験を行い、ヒトの視覚の検出限界を調べた。この光源系は、相関した1対の光子を発生させることができ、そのうちの1個は被験者の眼に照射され、もう1個は高感度カメラに照射された。毎回の試験では、1個の光子を含む光刺激と光が含まれていない光刺激が被験者に与えられ、いずれの刺激に光信号が含まれていたのかを被験者に回答させた。Vaziriたちは、合計30,767回の試験における被験者の成績をもとに、個人が1個の光子を含む小さな閃光と光子を含まない閃光を正しく識別する確率の平均値が偶然よりも高いことを明らかにした。


Human vision can detect single photons with a probability above chance, reports a study published online this week in Nature Communications. This result provides new insights into the detection limits of the human eye.

Studies in the 1940s have established that human subjects are capable of reporting light signals as low as a few (five to seven) photons. However, whether humans can perceive a single photon has remained an open question, partly because of experimental constraints connected to the light source used to generate photons in previous experiments.

Alipasha Vaziri and colleagues designed a single-photon light source using quantum-optic technologies and test the detection limits of human vision in three participants. The light source system is capable of generating a correlated pair of photons: one photon was sent to the participant’s eye, and the other towards a highly-sensitive camera. During each trial, participants were presented with two light stimuli, one of which contained a single photon and the other was blank (in other words, it contained no light). Participants were asked to state which of the two stimuli contained a light signal. Based on the performance of the individuals across a total of 30,767 trials, the authors found that the averaged probability of the individuals correctly identifying a small flash of light containing a single photon from a blank is above chance.

The authors note that the retinal and brain-circuitry mechanisms underlying their findings are the scope of future work.

doi: 10.1038/ncomms12172

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