Apr 1, And now Australian researchers have reported building the first ever quantum Fredkin gate – a type of logic gate thought to be the key to. Mar 26, The quantum Fredkin gate is a vital piece of quantum computing that was previously too complex to build, but scientists have found a way to. Mar 25, The quantum Fredkin gate, as shown in Fig. 1A, is a three-qubit gate whereby, conditioned on the state of the control qubit, the quantum states.

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Is it just a coincidence that retrosurf has posted immediately before or after that damnable spammer every time he has spammed the site? This claim does not contradict the claim of the previous paragraph, since storage proportional to the number of steps will require circuitry proportional to the number of steps, which will imply circuitry proportional to the amount that would be required if all feedback were eliminated.

Yes, but for some implementations like the mentioned Shors algorithm such a ‘regular’ computer would quickly reach limits e.

TomvanderZanden Measuring efficiency is a bit useless if you don’t specify what kind of efficiency. Further, decidability is unaffected by the computing platform that you use. Why are reversible gates not used?

The 0 and 1 bits swap places for each input bit that is set, resulting in parity bit on the 4th row and inverse of parity on 5th row. It is possible to emulate quantum logic with binary logic, just like it’s possible to water an entire soccer pitch by applying a single drop to each blade of grass with an eyedropper.


Those assumptions make these gates sound like a miracle solution. Your emulation, however, will not display the speed-ups that make quantum computing attractive.

Which is an interesting thing to know. A new paradigm in quantum information processing has been demonstrated by physicists at UC Santa Barbara. By signing up, you agree to our Privacy Policy. By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand ftedkin Terms of Service.

They demonstrated this by experimentally realising a challenging circuit—the quantum Fredkin gate—for the first time. It is universalwhich means that any logical or arithmetic operation can be constructed entirely of Fredkin gates. The team used particles of light. Reversible computing has freedkin studied since Rolf Landauer advanced the argument that has come to be known as Landauer’s principle.

And so there must be a meta truths to aggregate what once was taken as high fidelity. Feynman diagrams are applied in condensed matter physics.

Home Questions Tags Users Unanswered. So the question is what technical hurdles are still preventing their large scale usage. For any process that needs to change something you can only approximate equilibrium by making the change happen as slowly as possible. However, until now, no practical reversible logic gates have been demonstrated.

I’ve edited the post to say what would be required to use such a thing to do any meaningful work. Then again without these, mathematics itself maybe philosophically existential and with them the possibly Godelian axiomatic over flow becomes interesting.

Physicists demonstrate a quantum Fredkin gate

Scientists from Griffith University and the University of Queensland found a way to construct Fredkin gates while simplifying the amount of logic operations needed. This is a gate where two qubits are swapped depending on the value of the third.


Note that with the CMOS technology used in today’s computers, feedback is required to ensure that results reported by computations in different parts of a circuit are made available simultaneously to other parts, since if they weren’t the relative timing with which the signals arrive would constitute “information” which could not be perfectly passed downstream; other technologies might make it possible to have many gates propagate signals at precisely the same rate while retaining reversibility, but I know of no practical technology for that.

Share this article Copy link Link copied. Realistically programming a quantum computer uses true quantum logic frekdin only for specific instances of quantum algorithms.

Could a Fredkin gate be the next quantum leap forward for computing? –

The above recipe could be repeated any number of times to run the algorithm for an arbitrary number of steps; only the last step of the recipe wouldn’t be reversible. The initial question was “why aren’t these things used”. What is undecidable in conventional computation is still undecidable in quantum computing.

Of course you can emulate a quantum computer on a sufficiently power digital computer.

Physicists demonstrate a quantum Fredkin gate

Can this site sink lower? Another difficulty is that reversible logic gates must be both logically and physically reversible. Get journalism built for thinkers like you.