Precision requirements for spin-echo-based quantum memories

Abstract

Spin-echo techniques are essential for achieving long coherence times in solid-state quantum memories for light because of inhomogeneous broadening of the spin transitions. It has been suggested that unrealistic levels of precision for the radio-frequency control pulses would be necessary for successful decoherence control at the quantum level. Here we study the effects of pulse imperfections in detail, using both a semiclassical and a fully quantum-mechanical approach. Our results show that high efficiencies and low noise-to-signal ratios can be achieved for the quantum memories in the single-photon regime for realistic levels of control pulse precision. We also analyze errors due to imperfect initial-state preparation (optical pumping), showing that they are likely to be more important than control pulse errors in many practical circumstances. These results are crucial for future developments of solid-state quantum memories.

Prospective applications of optical quantum memories

“…dynamical decoupling). This was studied in [69] which showed that this within the reach of realistic levels of precision.…”

Room-temperature storage of electromagnetic pulses on a high-finesse natural spin-frequency comb

“…The influence of nonideal π pulses on the quantum efficiency and noise in free-space optical quantum memories has been discussed in [40]. It has been shown that n equalled pulses with pulse area π ± δ reduces the quantum efficiency due to the factor ∼(1 − n 2 N s δ 2 ).…”

Quantum Light Storage in Solid State Atomic Ensembles

“…The challenge lies in avoiding to populate the |s state with too many atoms, which would lead to spontaneous emission noise in the output when reading out the single spin excitation. At first this might appear to be almost impossible for a single excitation in |s [124], but it was shown later that the strong collective emission into a particular spatial mode of the stored single excitation provides a very effective spatial filtering of the spontaneous emission noise [125]. The spin-echo technique must be very efficient, however, to avoid this noise, and it remains to be seen if the storage fidelity of a single photon can be high enough when applying spin echo techniques.…”