# What is the hardware for quantum gates?

Gold Member
I have lots of materials on the theory of quantum gates in terms of matrices, linear operators, and so forth. However, I would like to gain a basic understanding of how these matrices are achieved in practice. The difference is between knowing that a transistor acts as a switching or amplifying device, and knowing that this is achieved by making a PNP or NPN semiconductor sandwich etc. Web sites which explain it in non-specialist terms (I view hardware as a sort of necessary evil for the theory to be applicable) are welcome, as long as they do not send me to a site that requires paid access. All that I have been able to glean from the Internet is that crystals are often used. I don't need too much detail, but more detail than that.... Thanks in advance.

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#### Greg Bernhardt

@nomadreid did you find any more insight on this topic?

Gold Member
Only some rather vague statements about using variable magnetic fields, but nothing specific.

#### f95toli

Gold Member
A "gate" is an abstract mathematical concept. How you actually implement the operation described by a sequence of gates depends entirely on what type of hardware you use.
The "gate" itself is very rarely a physical "thing" but rather a sequence of changes of a some set of parameters.That is, typically, you end up using a few different "control knobs" to implement a gate (microwave fields, laser light, magnetic or electric fields etc) , by adjusting these as a function of timeyou can implement a gate.

The simplest example of a gate would be a single pulse of some sort. For both spin-based and superconductor based qubits this will be a microwave pulse with a specific frequency, amplitude and length.

Note that all manipulation used in NMR/MRI would in the language of QC be described as "gate operations".

#### microsansfil

The linear optic can be used to develop quantum gate. For example, beam splitter can be used for Hadamard transformation.

/Patrick

"What is the hardware for quantum gates?"

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