The refrigeration system used to cool the processor

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The refrigeration system used to cool the processor is known as a “dry” dilution refrigerator. It uses liquid helium in a closed- loop cycle in which it is recycled and re- condensed using a pulse tube cryocooler. The closed-loop refrigeration removes the need for on-site replenishment of liquid helium and makes the system suitable for remote deployment. While dilution refrigerators are not uncommon in research environments, D-Wave has advanced the technology to ensure long life and high reliability. As the cooling power available at such low temperatures is extremely low, D-Wave has taken great care to minimize the heat loads and effectively manage the heat transfer within the system. Despite the extreme environment inside the system, the D-Wave quantum computer can be located in a standard data center environment. Temperature in Kelvin Starting at room temperature at the top, the temperature decreases at each level until it is close to absolute zero where the processor itself is located.
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©2015 D-Wave Systems Inc. All Rights Reserved. The I/O subsystem is responsible for passing information from the user to the processor and back. After receiving a problem from the user via standard web protocols, data is converted to analog signals and carried on normal conducting wires that transition to superconducting wires at low temperatures. The requirements for the I/O and shielding subsystems placed many unusual demands on the design, materials and manufacturing processes required. The I/O subsystem was designed to filter out essentially all unwanted noise, function at millikelvin temperatures and withstand multiple warming and cooling cycles between room temperature and base temperature. The current I/O system uses 200 heavily filtered lines from the control electronics to the processor that were specifically designed for optimal system performance. The system also includes a variety of superconducting metals which often require unusual and non-standard manufacturing techniques. In addition, none of the materials close to the processor can be magnetic. As the quantum processor is adversely affected by stray magnetic fields, extreme care had to be taken to exclude them. The magnetic shielding subsystem achieves fields less than 1 nanotesla across the processor in each axis. This is approximately 50,000x less than the Earth’s magnetic field. This low magnetic field environment is achieved with a system comprised of multiple shields, some of them high permeability metals and some of them superconducting. The system sits inside a shielded enclosure that screens out RF electromagnetic noise. The only path for signals between the inside and outside of the shielded enclosure is a digital optical channel carrying programming information in, and results of computations out. The processor resides in a high vacuum environment in which the pressure is 10 billion times lower than atmospheric pressure.
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  • Fall '13
  • Quantum computer, Qubit, D-Wave Systems Inc

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