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The Cryogenic Measurement Laboratories, located on the ground floor of the Newton Building at UNSW, house sophisticated experimental facilities for performing characterisation and measurements of nanoscale devices. The G12 laboratory is supervised by A/Prof Andrea Morello, and serves as the primary low-temperature measurement facility for the silicon qubit projects at UNSW.
This 150 m2 laboratory contains equipment capable of measuring voltage signals in the pV range, from DC to 50 GHz microwave frequencies. These measurements can be performed at temperatures ranging from 30 mK to room temperature, at constant magnetic fields up to 10 T. The laboratory is at present equipped with three dilution refrigerators with various configurations to enable a wide range of measurements. The laboratory is supported by two professional staff members with extensive experience in cryogenics and RF measurement systems.
Two of the dilution refrigerators are housed in an electrically screened room to allow highly sensitive measurements of two independent samples simultaneously. Two ‘RF’ dilution refrigerators have been configured to allow ultra-high speed measurements on picosecond timescales using radio frequency (200–600 MHz), fast pulse (30 ps) and microwave (0–50 GHz) techniques. A large array of supporting instrumentation is available. Microwave sources are used in conjunction with AWG arbitrary waveform generators for pulsed local electron spin resonance experiments. Real-time data acquisition and fast feedback techniques are available. All setups have ultra-low noise and high bandwidth current amplifiers, allowing detection of currents in the pA range with < 10 microseconds time resolution, or fA at low frequency. All 3 fridges allow applying gate pulses and operating multi-qubit devices. A large number of device dipping probes with associated data acquisition electronics allow for characterisation of devices at liquid Helium temperatures, enabling a variety of standard device tests to be performed. The tests include: DC transport, RF/microwave measurements and magnetic field studies. A new wideneck dipping Dewar has been purchased and installed, to allow easy dipping of larger and multi-gate sample boards, including high-frequency experiments.
RF/OPTICAL MEASUREMENT LABORATORY
Since joining UNSW in 2011, Prof Sven Rogge established a new 100 m2 laboratory at UNSW with focus on quantum measurements of devices with optical and RF input as well as fast gate control. Currently, devices can be evaluated at 300mK and above, 12T, with 40GHz microwave access, and gate lines with rise times down to 100ps. The latter allowed the demonstration of electron shuttling through a donor up to 3GHz. A low electron temperature is achieved by the use of optically isolated DC and pulse electronics developed in Delft. Recently, optical access to dopant devices was established at UNSW. This led to the first observation of resonant photo-ionization of a dopant atom by single shot charge sensing with 50neV resolution revealing the hyperfine structure. In 2013, dilution refrigerator has been installed in this laboratory, equipped with low noise DC electronics, high speed gates lines, and microwave capability.
RAPID DEVICE TESTING CRYOGENIC LABORATORY
During the last year Professor Simmons has further expanded the Centre’s measurement laboratories. A new cryogen-free dilution refrigerator has been installed, equipped with a large superconducting magnet, low noise DC electronics, high -speed gate lines, and microwave capabilities. The system has a unique ability to insert and remove experimental devices rapidly, allowing for fast measurement turnaround. This laboratory has been upgraded with UPS supported power supply, an improved Helium gas recovery network, Ersatz compressed dry air supply, a large cooling water capacity, and additional security and safety measures. Since the solid-state qubit measurements in the Centre are impossible without liquid helium, the Faculty of Science at UNSW recently purchased a helium liquefaction plant which now allows the use of Helium in a sustainable manner. This $2.1M investment allows measurements to run uninterrupted. The helium liquefier was installed and commissioned at the end of 2012, and has been operating successfully throughout 2013, serving the UNSW scientific community within the UNSW Faculty of Science with a reliable supply of liquid Helium. In 2013, the Centre laboratories were subject to a UNSW internal Workplace Health and Safety audit, and passed this with excellent results.