What are scientists inputting into a quantum computer and what are they getting out of it? I don’t understand what it’s ‘calculating’?
In: Mathematics
Not really a ELI5 explanation, but the following is how I understand it.
In a classical computer, a 32-bit register can contain one of 2^32 different states at any given time. Each bit can be either 0 or 1, representing a single, specific state out of the possible 2^32 states.
In contrast, a quantum computer uses quantum bits, or q-bits, which can represent multiple states simultaneously due to the principle of superposition. The state of 32 q-bits is a complex linear combination of 2^32 different states. This means that a 32 q-bit register can hold all 2^32 states at once, with each state having a certain probability amplitude. The squares of these amplitudes’ magnitudes add up to one, ensuring proper normalization.
One unique property of quantum states is that they can undergo a global “phase shift,” where applying the same rotation to all the probability amplitudes doesn’t change the measurable state of the system.
Quantum “gates” manipulate the state of q-bits through operations that can entangle q-bits, create superpositions, and perform other transformations. These operations are fundamentally different from classical logic gates and can process an immense amount of information simultaneously. Simulating these quantum operations on a classical computer would require exponentially more resources, highlighting the efficiency and power of quantum computation.
Finally, at the end of a quantum computation, a measurement is performed. This collapses the superposition into one of the possible states, and the result is probabilistic, influenced by the probability amplitudes of the states (look up “Born’s rule”).
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