How far off are quantum computers?

Are there any quantum computers in existence?

In September of 2020, IBM revealed they developed one of the largest existing quantum computers in the world (as of the time this blog post was published), consisting of 65 qubits. The company has already identified a number of areas in which the complexity of quantum computing capabilities may be applied.

Can quantum computers be built?

There are currently a number of significant obstacles to constructing useful quantum computers. It is particularly difficult to maintain qubits' quantum states, as they suffer from quantum decoherence and state fidelity. Quantum computers therefore require error correction.

How much is a quantum computer worth?

A startup based in Shenzhen, China, called SpinQ has unveiled a quantum computer that can fit on a desk — and it costs less than $5,000, as Discover Magazine reports.

How expensive is a qubit?

By most estimates, a single qubit costs around $10K and needs to be supported by a host of microwave controller electronics, coaxial cabling and other materials that require large controlled rooms in order to function. In hardware alone, a useful quantum computer costs tens of billions of dollars to build.

Does NSA have quantum computers?

In the FAQ, the NSA describes a Cryptographically Relevant Quantum Computer (CRQC) as a quantum computer that's capable of actually attacking real world cryptographic systems, something that's currently infeasible.

What can quantum computers not do?

Not having any ability for I/O of any sort, a quantum computer has no capability for controlling real-time devices, such as process control for an industrial plant. Any real-time control would have to be made by a classical computer.

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