Improvement of vacuum squeezing resonant on the rubidium D1 line at 795 nm

Abstract

Abstract:We report on efficient generation of second harmonic laser and single-mode vacuum squeezed light of 795 nm with periodically poled KTiOPO 4 (PPKTP) crystals. We achieved 111 mW of ultra-violet (UV) light at 397.5 nm from 191 mW of fundamental light with a PPKTP crystal in a doubling cavity, corresponding to a conversion efficiency of 58.1%. Using the UV light to pump an optical parametric oscillator with a PPKTP crystal, we realized -5.6 dB of a maximum squeezing. We analyzed the pump power dependence of the squeezing level and concluded that the UV light induced losses limit the improvement of the squeezing level. The generated squeezed light has huge potential application in quantum memory and ultra-precise measurement.

Generation of polarization squeezed light with an optical parametric amplifier at 795 nm

“…Then, the 397.5 nm UV laser is mode-matched to the OPA cavity. In our previous paper [29,30], we mentioned that strong grey tracking effect was observed at high UV power for both SHG and OPA process. To minimize the grey tracking effect, we restrict the UV power to around 50 mW.…”

“…For OPA cavity, the transmissivity of the output coupler is 11.5%. The detailed parameters of these three cavities can be seen in our previous paper [29]. The MC is used to filter the spatial mode of the local beam, ensuring a high interference visibility in the homodyne detection.…”

Polarization squeezing at the audio frequency band for the Rubidium D_1 line

“…Wolfgramm et al [13] obtained a squeezing of 3.6 dB at 1 MHz with the squeezing band ranging from 0.08-2 MHz; Wu et al [24] achieved a polarization squeezing of 4 dB at an analytical frequency of 3 MHz; whereas, Hé tet et al [25] obtained a squeezing of 5.2 dB, covering a frequency range, 150-500 kHz. Our group achieved a polarization squeezing of 5.6 dB at 2 MHz, with a frequency band ranging from 0.2-10 MHz [26]. However, these results are all in the high frequency range, far away from the audio frequencies, where additional noise coupling needs to be considered.…”

Deterministically entangling multiple remote quantum memories inside an optical cavity

“…Since in the fidelity formula the vacuum noise is normalized to 1, a coefficient 4 appears in the expressions of covariance matrices [56]. Thus quantum memory fidelities can be obtained from time-dependent operators [the above solutions (3) and (5) F (T 0 ) T on the transmissivity T of the input-output mirror and Raman excess noise V in the memory process with the 5 dB input squeezed state of light resonant with the atomic absorption line [57]. It can be seen that the performance of F (0) W and F (T 0 ) T can be increased when the transmissivity T of the input-output mirror is under the appropriate condition.…”

“…The squeezing parameters ri for all the OPAs are assumed to be identical for simplicity and are proportional to the nonlinear coupling strength κ and interaction time τ between the light and nonlinear crystal, ri = r = κτ . The squeezing parameter r = 0.6 is taken into account, which corresponds to the ∼5 dB squeezed state of light [57].…”