A "Photon Machine Gun" For Quantum Computers

An anonymous reader writes "Generating entangled photons in a reliable way is impossible right now, stalling the development of the optical quantum computers that would use entangled photons as quantum bits (qubits). Because entangled photons can only be produced at random — which takes time — the most powerful optical quantum computing device use only 6 qubits. UK and Israeli quantum physicists have designed a blueprint for a 'quantum machine gun' that fires out barrages of entangled photons on demand. They think within a few years this device will be built, and could lead to quantum computing using 20 to 30 qubits. Every additional qubit doubles the computing power, so these quantum computers could outperform any existing classical computer, the researchers say. The quantum machine gun is described as 'one of the most exciting theoretical proposals I've read in five years' by a leading quantum physicist." The research was published in Physical Review Letters earlier this month.

Comments

Re:Not particularly useful against an insurgency

[Shadow of Eternity]

Harmful harmful force? Dude i think you need to re-evaluate your worldview if you want to blame the group being constantly attacked and threatened with the explicit goal of genocide for everything wrong. The mere presence of jews in the middle east produces the reaction you see from Hamas and friends, whether or not Israel was officially a state would have fuck all to do with anything other than the success of those attempts at genocide.

Hell Hamas' own govt charter explicitly blames the jews (merchants of death) for everything from the french and russian revolutions to both world wars while outright demanding the death of every jew and anyone who refuses to participate in said genocide.

Re:Explain the hype, please?

[maxwell demon]

Ok, I just wrote a lengthy reply, and then by accident hit "refresh", and all the text was gone :-(

Therefore here the short version:

• The speedup is basically because for quantum systems the dimension of the configuration space grows exponentially rather than linearly with the size of the system (i.e. number of qubits). The fact that we can't simply measure the complete state is actually a limitation, because it means we cannot directly access an arbitrary unknown state.
• You can do quantum computing by just doing measurements because every measurement modifies the measured system, and with entangled states, this change is non-local (i.e. you also modify parts of the system where you didn't just destroy any entanglement by your measurement). However you need special entangled states to do universal measurement-based quantum computing (i.e. to allow arbitrary transformations with measurement only); one state which works is the cluster state produced by this "photon machine gun"
• They didn't claim that qubits revolutionize storage, but that if emulating the 20 to 30 qubit quantum computer on a classical computer, it would not fit into computer storage. However I doubt that; storing the state of 30 qubits needs about 16 GB, which is large, but perfectly doable in todays computers (and may be actually standard by the time this photon gun is realized). The problem with simulating the quantum computer would not be storage, but time.