Towards Experimental Implementation of Quantum Gate Operations in a 28 Si:P Sample

 

Quantum information theory predicts a major speedup in several important processing tasks, which makes it a subject of great interest. However, the search for a physical system in which such quantum information processing algorithms can be successfully executed, is still underway. One possible implementation of a quantum information processing unit may be achieved by directly addressing electron spins in a solid-state sample, using methods of induction detected pulsed electron spin resonance (ESR). En-route towards experimental implementation of unitary operations (quantum logic gates) on electron spin states, employing methods of pulsed ESR, the detection sensitivity that is available in state-of-the-art ESR systems has to be improved significantly. We present experimental results that were recorded in our ultrasensitive induction-detection ESR setup, with a sample of phosphorus doped isotopically pure silicon crystal (28Si:P), showing such an improvement in detection sensitivity. We estimate that the number of electron spinsrequired for a detectable signal in our new setup is only ~ 104 spins/√Hz (meaning ~100 spins in a few hours of averaging time), which is 5 orders of magnitudes lower than in the most sensitive commercial ESR setup.This high sensitivity was achieved thanks to the development of an ultra-miniature micrometer-sizedmicrowave resonator that was operated at 34 GHz at cryogenic temperatures in conjunction with a unique cryogenically cooled low noise amplifier.