My laptop works fine at room temperature, but I’ve heard real quantum computers need to be cooled down to just a few hundredths of a degree above absolute zero (colder than Antarctica!). Why can’t they just work warm like regular processors? And wont they generate heat as well? How is this so precisely controlled?
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Qubits are extremely unstable as they rely on quantum superposition (basically the qubit can be both a 0 and a 1) which can be very easily collapsed into a 0 or 1. Temperature is minimized to reduce the vibration of the qubits so it doesn’t collapse easily. Stability is one of the biggest problems in quantum computing and is essentially is the last hurdle until the technology becomes viable for actual use.
Because heat is noise and noise is the enemy of quantum computers. You are essentially doing an extremely sensitive measurement in a quantum computer and you are limited by how large your error is, more noise, more error, less useful your quantum computer is. In fact quantum computers that exist today can’t really do any useful calculations, and one of the big reasons is that the error is too large. Improving error correction is where the current big improvements are being made on the road to practically useful quantum computer, but having minimal error to start with is of course preferrable and that means minimal heat.
I don’t know the specifics of quantum computing, but usually needing to be that cold comes from needing superconductive materials. Cooling things down that cold reduces their resistance to like 0.1% or less compared to normal materials and allows massive amounts of power to be run through them. If they send that power through normal circuits, they would likely instantly melt from the waste heat generated.
Because of superconductivity. With computers like these, it’s important for there to be effectively zero resistance in the “wires” that physically connect the components. So far, we can only achieve the requires superconductivity at very very very low temperatures. The search for “room temperature superconductors” has been going on hot and heavy for half a century now and so far we haven’t seen serious success – but the quantum computers may be able to process models that might be able to calculate how to do it. Hopefully.
Room temperature superconductors would lead to more immediate revolutionary improvements to life than quantum computers will. Like, did you know that there’s really no problem generating enough energy for the world’s needs, even from green energy sources like for example solar farms in the most intensely sunny parts of the world. The problem is really with distributing that power without losing too much of it and converting it right back into heat. Cheap room temperature superconductors could remedy that problem – and tremendously reduce the energy required to do many things like transportation and phones etc.
“Colder than Antarctica” is as technically correct as saying Julius Caesar died more than a month ago.
We’re talking about temperatures colder than the vacuum of space
Quantum computers have to be kept extremely cold because the tiny particles they use, like electrons or photons, need to stay in a super fragile state called a quantum state. This is the state where all the cool quantum magic like superposition and entanglement happens, and it’s really easy to mess up.
At warmer temperatures, there’s too much random motion (called thermal noise) from particles bumping into each other. That noise can knock the quantum bits (qubits) out of their delicate states and ruin the calculations. So, we cool them down to near absolute zero to keep them calm and stable.
People have answered the question pretty well for the most part, but there’s challenge to the premise that needs to be made: not all quantum computers need extremely cold temperatures. Silicon spin qubits need cold temperatures, but not the near-zero Kelvin temperatures needed for superconducting ones, and certain light-based quantum hardware can operate at near room-temperature.