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SUMMARY:Coherence and coupling of GaAs two-electron spin qubits - Prof. He
 ndrik Bluhm\, RWTH Aachen\, Germany
DTSTART:20120322T141500Z
DTEND:20120322T151500Z
UID:TALK37079@talks.cam.ac.uk
CONTACT:Chris Ford
DESCRIPTION:Semiconductor spin qubits are promising candidates for quantum
  computation because of their slow decoherence and potential for scalabili
 ty. All fundamental single qubit operations have been demonstrated for GaA
 s based spin qubits\, but they suffer from decoherence due to hyperfine co
 upling to nuclear spins. We have developed effective techniques to mitigat
 e this decoherence channel for two-electron spin qubits in double quantum 
 dots.\n\nBy repeatedly inverting the qubit in a way that decouples its evo
 lution from the fluctuations of the nuclear spin bath\, its coherence time
  can be extended to more than 200 us\, two orders of magnitude longer than
  previously shown. Alternatively\, operating the qubit as a feedback loop 
 that controls the nuclear bath also enhances the coherence time and enable
 s universal single qubit control with greatly improved gate fidelities.\n\
 nHaving achieved good single qubit control\, a fundamental milestone is to
  couple qubits in order to generate entanglement. We demonstrate a protoco
 l to implement two-qubit gates using the Coulomb interaction between adjac
 ent double dots while decoupling both qubits from slow electrical fluctuat
 ions. These results indicate that Bell states can be created with sufficie
 nt fidelity to demonstrate entanglement.\n
LOCATION:Small Lecture Theatre\, Cavendish Laboratory\, Department of Phys
 ics
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