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Thursday, October 22, 2009
12:30 PM - 1:30 PM
T-DO Conference Room (TA-3, Bldg 123, Room 121)

Quantum Lunch

Quantum-Limited Measurements: From Dark Matter to Qubits

Darin Kinion
Lawrence Livermore National Laboratory

Like all measurement devices, the linear microwave amplifier is subject to the Heisenberg Uncertainty relation. As a result, noise-free amplification is impossible and there is a minimum noise temperature which such an amplifier can achieve. This Standard Quantum Limit, corresponding to a noise temperature of 50 mK at 1 GHz, is an order-of-magnitude lower than the noise temperature of state-of-the-art GaAs HEMTs. We have developed a new type of microwave amplifier based on a Superconducting Quantum Interference Device (SQUID) which has a noise temperature within 20% of the SQL. This has opened the door to a range of experiments exploring the fundamentals of measurement as well as dramatically improving existing experiments. I will describe a couple of applications for the quantum-limited amplifier: a search for dark-matter axions underway at LLNL and an effort to perform fast readout of superconducting qubits to explore the dynamics of quantum mechanical systems.

Host: Gennady Berman