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rollingstein
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While reading up the recent hoopla about DWave's new "Quantum Computer" I came across a practical question about cryogenics:
How long could you keep a 10 kg mass at below 80mK without any external cooling if you could design the best practical insulation system? DWave claims it is "several months to years" but I was a bit skeptical. Assume you can use a 10'x10'x10 cube at most to contain it and heat loss is to ambient air.
Could one really make insulation that good? What do ballpark heat flux numbers show? Since DWave sells the darn thingy for $15 Million I'll assume we are allowed access to the best possible material / vacuums etc.
If you really care, say you get an awesome budget of $1 Million to build your insulating system! :)
More details:
http://www.dwavesys.com/en/dev-tutorial-hardware.html
Reduction of the temperature of the computing environment below approximately 80mK is required for the processor to function, and generally performance increases as temperature is lowered - the lower the temperature, the better. 20mK is targeted as the lowest temperature that can be easily reached as an operating point. The processor and parts of the input/output (I/O) system, comprising roughly 10kg of material, must be cooled to these temperatures. Most of the physical volume of the current system is due to the large size of the refrigeration system. The refrigeration system used to cool the processors is known as a dilution refrigerator.
The inset in Figure 7 shows the chip packaging attached to the cooling apparatus. Note that the area around the chip has now been closed up to protect it from being damaged. When the computer is being operated, this part is sealed inside a vacuum chamber Because quantum processors require low temperatures for the quantum effects to be sustained, the entire piece shown in the inset of figure 7 is cooled to around 20mK, which is approximately 100 times colder than interstellar space.
To reach the near-absolute zero temperatures at which the system operates, the refrigerators use liquid Helium as a coolant. The type of refrigerator inside the D-Wave OneTM system is known as a "dry" dilution refrigerator. This means that all the liquid helium resides inside a closed cycle system, where it is recycled and recondensed using a pulse-tube technology. This makes them are suited to remote deployment, as there is no requirement for liquid helium replenishment on-site.
The specialized equipment to allow cooling to these temperatures is available commercially and runs reliably. The refrigeration technology is also mature enough that the system has a turnkey operation. The computer can be cooled down to operating temperature within several hours, and once this temperature is reached remain cold for months or years.
How long could you keep a 10 kg mass at below 80mK without any external cooling if you could design the best practical insulation system? DWave claims it is "several months to years" but I was a bit skeptical. Assume you can use a 10'x10'x10 cube at most to contain it and heat loss is to ambient air.
Could one really make insulation that good? What do ballpark heat flux numbers show? Since DWave sells the darn thingy for $15 Million I'll assume we are allowed access to the best possible material / vacuums etc.
If you really care, say you get an awesome budget of $1 Million to build your insulating system! :)
More details:
http://www.dwavesys.com/en/dev-tutorial-hardware.html
Reduction of the temperature of the computing environment below approximately 80mK is required for the processor to function, and generally performance increases as temperature is lowered - the lower the temperature, the better. 20mK is targeted as the lowest temperature that can be easily reached as an operating point. The processor and parts of the input/output (I/O) system, comprising roughly 10kg of material, must be cooled to these temperatures. Most of the physical volume of the current system is due to the large size of the refrigeration system. The refrigeration system used to cool the processors is known as a dilution refrigerator.
The inset in Figure 7 shows the chip packaging attached to the cooling apparatus. Note that the area around the chip has now been closed up to protect it from being damaged. When the computer is being operated, this part is sealed inside a vacuum chamber Because quantum processors require low temperatures for the quantum effects to be sustained, the entire piece shown in the inset of figure 7 is cooled to around 20mK, which is approximately 100 times colder than interstellar space.
To reach the near-absolute zero temperatures at which the system operates, the refrigerators use liquid Helium as a coolant. The type of refrigerator inside the D-Wave OneTM system is known as a "dry" dilution refrigerator. This means that all the liquid helium resides inside a closed cycle system, where it is recycled and recondensed using a pulse-tube technology. This makes them are suited to remote deployment, as there is no requirement for liquid helium replenishment on-site.
The specialized equipment to allow cooling to these temperatures is available commercially and runs reliably. The refrigeration technology is also mature enough that the system has a turnkey operation. The computer can be cooled down to operating temperature within several hours, and once this temperature is reached remain cold for months or years.
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