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arXiv · 1101.5198

Phase shift spectra of a fiber-microsphere system at the single photon level

Akira Tanaka·Takeshi Asai·Kiyota Toubaru·Hideaki Takashima·Masazumi Fujiwara·Ryo Okamoto·Shigeki Takeuchi
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Abstract

We succeeded in measuring phase shift spectra of a microsphere cavity coupled with a tapered fiber using a weak coherent probe light at the single photon level. We utilized a tapered fiber with almost no depolarization and constructed a very stable phase shift measurement scheme based on polarization analysis using photon counting. Using a very weak probe light (\bar{n} = 0:41), we succeeded in observing the transition in the phase shift spectrum between undercoupling and overcoupling (at gap distances of 500 and 100 nm, respectively).We also used quantum state tomography to obtain a 'purity spectrum'. Even in the overcoupling regime, the average purity was 0.982 \pm 0.024 (minimum purity: 0.892), suggesting that the coherence of the fiber-microsphere system was well preserved. Based on these results, we believe this system is applicable to quantum phase gates using single light emitters such as diamond nitrogen vacancy centers.

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Akira Tanaka, Takeshi Asai, Kiyota Toubaru, Hideaki Takashima, Masazumi Fujiwara, Ryo Okamoto, Shigeki Takeuchi. 2011-01-27. Phase shift spectra of a fiber-microsphere system at the single photon level. https://doi.org/10.1364/oe.19.002278

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