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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If one only needed to run a few thousand cycles at a time reversibly, capture the results, rewind the cycles, and then replace the previous initial state with the captured results, that might almost be workable, but would be monstrously complex. IBM is one of several companies working on developing quantum computers. I am by no means an expert on this topic, but just from casually reading Wikipedia: Inputs on the left, including two constants, go through three gates to quickly determine the parity.

However, if larger bricks are used the same wall could be built with far fewer bricks ,” said Dr Raj Patel, one of the lead scientists behind the breakthrough. Pryde, Science Advances, 25 MarVol.

Here’s an interesting question: March 26, By Corey Fedde Staff. I was reading the book “The singularity is near” written gste Kurzweil and he mentioned the reversible gates like for example the Fredkin gate. The advantage using such gates is that we could get rid of the thermal waste related to computation where bits just disappear into heat, and computation won’t need any energy input.

So the question is what technical hurdles are still preventing their large scale usage. No end to the nonsense. Researchers from MIT and elsewhere have recorded, for the first time, the fedkin coherence” of a graphene qubit—meaning how long it can maintain a special state that allows it to represent two logical states simultaneously.

computer architecture – Why are reversible gates not used? – Computer Science Stack Exchange

However, until now, no gage reversible logic gates have been demonstrated. The initial question was “why aren’t these things used”. Their advance, described in a paper published this week in Frekin You still need an operating system for the human operator.


I also think it is a shame that I never heard about those gates in my electrical engineering bachelor and master studies at a top German university Additionally, we estimate the energy dissipation of the gate, and discuss the minimum energy dissipation required for reversible logic operations.

Reversible circuits also don’t need to be adiabatic; practical reversible gates have been made which are no slower than non-reversible chips taking into account that reversible chips are usually larger, and therefore have a speed of light latency increase. Another basic point is that anytime energy dissipation is decreased on a chip, it’s essentially moving the gate system to “more reversible”, and lower-energy chip dissipation has been a high priority for a long time now in mobile computing representing a sort of industry-wide paradigm shift.

Most of quantum computing can be seen to be attempting to create reversible qubit gates and it’s very hard experimentally to match the theoretical properties of the QM formalism, but steady progress is being made. We’ve got non-quantum computers trying to design a quantum computer. 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.

However, if larger bricks are used the same wall could be built with far fewer bricks,” said Dr Patel. The more complex the operation and the more independent variables need to be simulated, the more processing power is required. 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 simplify the process.

Note that quantum computation is very much about reversible gates that’s part of what “unitary” means. By leveraging the good ideas of the natural world and the semiconductor Might as well ream them up the butthole with some spam! I think you ignore the requirement that the required tape length is proportional to the number of steps to be performed reversibly.

Monitor Daily Current Issue. This corresponds nicely to the conservation of mass in physics, and helps to show that the model is not wasteful.

That could get us gains till Are you referring to reversible optical chips? Since the system including all but the largest cartridges would have less thangte, that’s more than a million cycles per day per transistor.

Fredkin gate

If one is allowed to have outputs which are ignored if, given proper input conditions, they will never go high, then it might be possible to design a system that would, in theory, benefit from reversible logic. The C input is mapped directly to the C output. Usable feedback circuits must contain sections whose total number of inputs counting both the ones that are fed back from outputs and those that aren’t exceeds the number of outputs which are fed back to input the only way the number of inputs wouldn’t exceed the number of fed-back outputs would be if the circuits didn’t respond in any way to outside stimuli.


Now you have one in your pocket. I’ve edited the post to say what would be required to use such a thing to do any meaningful work.

Da Schneib Is emulated classical computation of quantum computation is the same? By turning highly bate equations into sets of simple diagrams, the method has established itself as one of the sharpest tools in a theoretical physicist’s toolbox. TomvanderZanden Measuring efficiency is a bit useless if you don’t specify what kind of efficiency. A quantum computer would be able to solve in one second a problem that could stump a traditional computer for 10, yearsHartmut Neven, director of engineering at Google, said.

There’s a photograph of that reversible-logic CPU at cise. If I remember my thermodynamics correctly, you can make the energy of a reversible computation arbitrarily small, but the minimum action energy times time must be a small constant. Further, the LIFO would have to be large enough to hold the state data for enough steps that the any energy cost of using it was less than the amount of energy it dredkin saved.

Fredkin gate – Wikipedia

I think we have more to worry about vate conventional AI in the hands of corporations than we do from quantum computing in the hands of governments or corporations. I wouldn’t have given it a second thought. Note that from a CS perspective, it’s trivial to make a computing process reversible if one has initially-empty storage medium whose size is essentially proportional frdkin the number of steps times the amount of state that could change in each step.