[RobC (OP)]

After many decades of development has a working quantum computer that lives up to the claims made for it actually operating?

[tkadm30]

I strongly believe the brain constitute a powerful quantum computer. Hypercomputation in brain activity is perhaps a (non-computable) physical evidence of synaptic quantum tunnelling. The self-organized criticality of neuronal and synaptic activity (exocytosis) may imply macroscopic quantum coherence inside neurons. Thus, the biological mecanism of quantum interference inside neurons may explain how hypercomputation of conscious states mediate consciousness.

[evan_au]

After many decades of development has a working quantum computer that lives up to the claims made for it actually operating?

Last I heard, the largest number factored by a quantum computers is 56,153=241 x 233
http://phys.org/news/2014-11-largest-factored-quantum-device.html

Factoring numbers has attracted a lot of attention because it could potentially be used to crack encryption.

If so, we are not likely to hear about it soon. Last year, DARPA reportedly spent $70M on quantum computers. The NSA budget is unknown, but as soon as DARPA uncovers something interesting, you can be sure NSA will spend far more than DARPA.

There are a variety of other potential quantum algorithms known, see: https://en.wikipedia.org/wiki/Quantum_algorithm

But perhaps numerical problems are not necessarily best suited to quantum computers. Perhaps solving quantum problems like determining the probability density of an electron in an atom, or the shape of a molecule might be better suited to a quantum computer?

[RobC (OP)]

I am inferring from the answers that it is a "no".

I heard once that the chances of getting a working quantum computer were a lot higher than harnessing fusion reactions. A estimate of 2040 was speculated for a fusion reactor and 2020 for a quantum computer.

So its a wait and see.

[alimeeabey]

Quatum and Silicon industry are growing very fast mainly because of the rapid technological changes.

[syhprum]

I don't think we will have to wait till 2020 progress is very fast, is it possible to run a simulation of a quantum computer on a large conventional computer if so is there any gain ?

[evan_au]

Last weekend I ran into a researcher working on quantum computers.
I asked him how many qubits they had achieved with quantum computation?
He said 1, maybe 2.

That won't be cracking my password any time soon.

[marlenewiley]

I heard the computer is a strong quantum. Quantum are very fast growing technology. Technological rapid changes this industry. Neuronal and synaptic activity are self organized. Please tell me a quantum computer on a large conventional computer?

[evan_au]

Most quantum computers require a large laboratory, and require refrigeration with liquid helium. Not cheap or convenient!

But it is possible to simulate a small quantum computer on a home computer. There are a number of sources - see here for a list:
https://quantiki.org/wiki/list-qc-simulators

Bear in mind that an 80-qubit quantum computer (if you could build and control such a thing) would in theory have more processing power than a conventional computer using every atom in the universe.

So don't expect a simulation of a quantum computer to handle many qubits, or to be very fast. I saw one that claimed to handle up to 22 qubits. See: http://www.quantumplayground.net/#/home

You can expect a steep learning curve if you want to write a program using qubits.