stayquantum mechanicsMedium,quantum fluctuation (English: quantum distortion. orQuantum vacuum fluctuation，Vacuum fluctuation）Is onspaceTemporary change of energy at any position[1]。fromWerner Heisenberg OfUncertainty principleThis conclusion can be deduced.
First of all, what is fluctuation? For example, we measured the length of a match stick ten times, and each time it may be different. It is recorded as
The deviation of each measurement from the measured average value is described.Sometimes we want to use an indicator to describe the deviation from the measured average. The most direct idea is to use the average, that is
However, since each deviation is random, the average deviation so defined is 0.A reasonable definition is to average the size of deviation. The so-called deviation size is
deviate
The absolute value of.This can be seen as square before square:
Why not use it directly
Because it is wrong to do so,
The dimension of is the area, and the length is the square root.Considering that we measured ten times, the magnitude of the deviation
Defined as:
In the above example, each timemeasureDeviation of
Officially began to explain what quantum fluctuations are.First, quantum mechanics studies the wave function:[2]
If we measure the position of the particle, we don't know where the particle is. We only know that the probability density of the particle at position x is
。Average position
namely:
In quantum mechanics, it is possible for particles to appear at any position. At this time, the deviation from the average position is:
It can be positive or negative. For the above equation, the average quantum mechanics is 0,
What is significant is the magnitude of the deviation, that is, the absolute value:
You can do it first
Square, then find the average of quantum mechanics, and then squareNote 2：
The deviation of position from the average value of quantum mechanics is also called fluctuation, and the magnitude of fluctuation is determined by
Characterized by the wave function, which is the essential feature of quantum mechanics
So we call this fluctuation quantum fluctuation.
significance
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Quantum fluctuations seem to violateconservation of energyHowever, this fluctuation occurs anywhere in space, and the energy exists for a very short time. When the time comes, it will disappear, so on a large scale, the law of conservation of energy has not been broken.However, at the end of the 1960s, someone thought of a possibility: the gravity of matter or energy itself has negative energy (because gravity is suction, assuming that the potential energy at infinity is 0, then when an object approaches, its potential energy is negative because of the work done by gravity).When the energy generated by fluctuations is generated, it generates a gravitational field. The negative energy of gravity and the corresponding positive energy of matter (or energy itself) cancel each other, making the whole system seem to have no more energy, so quantum fluctuations do not violate the law of conservation of energy.[1]
Correlation algorithm
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Quantum annealing(English:Quantum annealing）It is a kind of quantum fluctuationSubempirical algorithmThe global optimal solution can be found when the target equation has multiple sets of candidate solutions.Quantum annealing is mainly used to solveDiscrete spaceProblems with multiple local minima (combinatorial optimization problems), such as findingSpin glassThe ground state of.
Quantum annealing starts with the superposition of all possible states (candidate states) with equal weight, and then, the systemSchrodinger equationEvolution.According to the time dependent strength of the transverse field, the quantum tunneling between states is caused, which causes the probability amplitude of all candidate states to change constantly, and realizes quantum parallelism.If the change rate of the transverse field is slow enough, the system will maintain a ground state close to the instantaneous Hamiltonian, that is, adiabatic quantum computation.If the change speed of the transverse field is accelerated, the system may leave the ground state temporarily, but it has a higher possibility under the ground state of the final problem Hamiltonian, that is, diabatic quantum computing.The transverse field is finally closed, and the system is expected to reach the originaloptimization problem The solution ofising model The ground state of.After the initial theory was proposed, there was an experimental proof of the success of quantum annealing of random magnets.
