Purifying qubits in NMR quantum information processing

Recording Details

Speaker(s): 
Scientific Areas: 
PIRSA Number: 
07060015

Abstract

Any implementation of  a quantum computer will require the ability to reset qubits to a pure input state, both to start the computation and more importantly to implement fault-tolerant operations.  Even if we cannot reset to a perfectly pure state, heat-bath algorithmic cooling provides a method of purifying mixed states.  By combining the ability to pump entropy out of the system through a controllable interaction with a heat bath and coherent control of the qubits, we are able to cool a subset of the qubits far below the heat bath temperature.  Here we show an implementation of this cooling in a solid state NMR quantum information processor which offers high fidelity control of the qubit system and controllable access to a heat bath.   We demonstrate an implementation of multiple rounds of heat-bath algorithmic cooling on three qubits and discuss the improvements in control techniques which have allowed us to show the purification of a single qubit to one and a half times the heat bath polarization.