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Anneal name field

my last video explained how quantum annealing relates to the other forms of quantumly beauty and also the kind of problems quantum annealing so lots in this video I'm going to explain how the quantum annealing processor actually works so let's start by looking at single qubit now qubit can be in a state of either 0 or 1 and these states are encoded in a circulating current and a corresponding magnetic field now because of cube it's a quantum object it can be in a superposition of the zero state in the one state at the same time and in the quantum annealing process what happens is the each qubit goes from this superposition state into either the zero state or the one state which are classical States at the end of the anneal and the physics of this process can be shown in an energy diagram to begin with there's just one Valley and the lowest point corresponds with the superposition state of the cubit and when quantum annealing is run a barrier is raised and this turns the energy diagram into what's known as a double well potential here the low point of the left Valley corresponds to the zero state and the low point on the right valley corresponds to the one state now the cubic will end up in one of these valleys at the end of the anneal but how does it decide which one well well everything else being equal the probability of the qubit ending in the zero or the one state is even as for 50% trying to land in either state and the interesting thing is you can actually control the probability of it falling into the zero or one state which is done by applying an external magnetic field to the qubit the effect of this is to tilt the double well potential increasing the probability of ending up in the lower well this external magnetic field is called a bias and the qubits basically minimizing its energy in the presence of this external magnetic field okay so being able to control the probability that a qubit will fall into the zero of the one state is a really useful feature but the real power of these processors comes when you start linking them together and they can start influencing each other this is done with a device called a coupler and a coupler basically defines how qubits influence each other so a coupler can make the two couple qubits want to end up in the same state so that's either both 0 or both 1 the coupler doesn't care which one of these it is as long as the qubits end up with the same status each other or alternatively the coupler can make the neighboring qubits want to be in the opposite state so either 0 1 or 1 0 when you've got a coupling between two qubits you're now using another phenomena in quantum physics called entanglement when two qubits are entangled they now have to be considered as a single object but now which has got four states so you can imagine a potential with four states each one corresponding to a different combination of the two qubits and the relative energies of these states depend on the biases on each qubit and the coupling between them now when I said that the coupler wants the qubits to be the same or wants them to be opposite what I really mean is the couplers are making those states energetically favorable so if the coupler wants the two qubits to be the same really what it's doing is lowering the energy of those two states in comparison to the other states and if the coupler wants them to be opposite then it's lowering the energy of those states each qubit can have a bias applied to it and the qubits can interact other couplers and as a user you can actually choose all the values for these biases and couplers both the direction of them and also the strength and this is basically how you program a quantum computer you choose a whole set of biases a whole set of couplings that defines an energy Lance and then the quantum annealer does quantum annealing to solve and find the minimum energy of that energy landscape so now you can start to see some of the complexity of these machines with two qubits I've got four states I can define an energy landscape over if I go up to three qubits the number of states goes up to eight and for each extra qubit I add I actually double the number of states I can define this energy landscape over so the number of states goes up exponentially with the number of few bits and specifically that relationship is two to the power of n where n is the number of qubits okay so let me summarize what I've talked about so in quantum annealing you start off with a large set of qubits and each qubit is in a superposition state of 0 & 1 and also they're not connected yet then they undergo the quantum annealing where the couplings and the biases get introduced and the qubit all become entangled this large quantum object then changes the probability that each qubit will end up in the 0 1 state and then finally at the end of the nail each qubit ends up as either 0 or 1 and this final state is the minimum energy state of your problem or one very close to it and all of this happens in our chips in around 20 microseconds