Abstract
The signal-to-noise contrast of the optical readout in broadband Raman quantum memories is analyzed as a function of the pulse widths and phase properties of tailored optical field waveforms used to write in and read out broadband photon wave packets. Based on this analysis, we quantify the tradeoff between the readout contrast and the speed of such memories. Off-resonance coherent four-wave mixing is shown to provide a source of noise photons, lowering the readout contrast in broadband Raman quantum memories. This noise cannot be suppressed by phase matching, but can be radically reduced with a suitable polarization arrangement and proper field-waveform tailoring.
Highlights
Optical quantum memories – systems capable of storing and maintaining quantum states of light, releasing them on demand – are of central importance for the emerging photonic quantum technologies1,2
Raman scattering provides an ideal write-in/ read-out protocol for such broadband quantum memories17–19, allowing the quantum states of photons to be mapped onto molecular modes in gases or phonons20 in solids and enabling two-mode entanglement between light and relatively long-lived molecular or phonon modes in matter21–23
We will demonstrate that this noise cannot be suppressed by phase matching, but can be reduced by many orders of magnitude with suitable polarization arrangements and proper field-waveform tailoring
Summary
In the opposite limiting case, when the bandwidths of the laser pulses Δp, Δs, and Δr are much broader than the linewidth Γ, Eq [15] with |γ| as defined by Eq [12] with |χ2/χ1| ≪ 1 leads to ( ) R(ω, z) In this case, the contrast of the anti-Stokes readout signal relative to the FWM background is a factor of (Δ2p + pulses, Δ2s )/Γ2 lower (Figs 3 and 4) 10-THz operation rates can than its nominally highest value, σ0 be achieved for solid-state quantum.
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