Research ArticlePHOTONS

Optical π phase shift created with a single-photon pulse

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Science Advances  29 Apr 2016:
Vol. 2, no. 4, e1600036
DOI: 10.1126/sciadv.1600036


  • Fig. 1 Experimental procedure.

    (A) Scheme of the experimental setup. Signal light (red) illuminates an atomic gas. Two additional beams (blue) provide EIT-coupling light, one copropagating and the other counterpropagating the signal light. Dichroic mirrors (DMs) overlap and separate the beams. The polarization of transmitted signal light is measured using wave plates (WPs), a polarizing beam splitter (PBS), and avalanche photodiodes (APDs). (B) Level scheme. The 780-nm signal light couples states |g〉 = |5S1/2, F = 2, mF = −2〉 and |e〉 = |5P3/2, F = 3, mF = −3〉. The 480-nm EIT-coupling light couples states |e〉 and |r〉 = |nS1/2, F = 2, mF = −2〉, with nc = 69 and nt = 67 for control and target pulse, respectively. (C) Timing sequence of input powers of coupling light Pc and signal light Ps. The control pulse is stored in the medium, the target pulse propagates through the medium picking up a π phase shift if a control excitation was stored, and, eventually, the control excitation is retrieved.

  • Fig. 2 Rydberg-EIT spectra without control pulse.

    (A and B) The transmission Embedded Image and phase shift φ0 of the target signal beam are shown as a function of the signal detuning Δs. The line in (A) shows a fit based on Eq. (3). The line in (B) shows the expectation from Eq. (3) for the parameter values obtained in (A). For further experiments, we choose Δs/2π = −10 MHz (arrow), which is near the minimum of φ0. (C and D) For reference, similar spectra are shown in the absence of coupling light. All error bars in this article represent a statistical uncertainty of ±1 SD.

  • Fig. 3 Controlled phase shift.

    (A) The phase shift φ0 in the absence of a control pulse (blue circles) depends linearly on atomic density, so does the phase shift φ1 in the presence of a control pulse (green squares) but with a different slope because of Rydberg blockade. (B) The difference between the two phase shifts yields the controlled phase shift φ1 − φ0, which is equal to 3.3 ± 0.2 rad for the rightmost data point. The lines show linear fits.

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