学术文献库

Quantum memories for quantum communication need to be able to store photons for an extended time and then to release them on demand. This can be achieved in atomic frequency comb ensemble based quantum memories by control pulses that transfer the excitation to and from long-lived spin states. However, such pulses can give rise to coherent and incoherent noise due to their interaction with the memory ensemble. In this article, we experimentally demonstrate the ability to switch off the coherent noise from such control pulses during the echo emission in a spin-wave quantum memory, using the linear Stark effect in rare-earth-ion doped crystals. By applying an electric field pulse, the echo emission was coherently switched off prior to the first spin transfer pulse, and the stored data pulse was restored only when both an optical recall pulse and a re-phasing electrical pulse were applied, giving a high degree of control of both desired and undesired emissions. We estimate the effectiveness of this technique by turning off the free induction decay of a narrow ensemble of ions. This technique can thus improve the noise performance of spin-wave storage at the single photon level by quenching coherent optical radiation created by the strong control pulses. The method demonstrated here represents a proof-of-principle that the spin-wave storage scheme can be combined with Stark control. The combined scheme serves as an addition to the toolbox of techniques that can be used to realize a full version of a quantum repeater.