Tag: quantum computing

Speed limits of quantum computing found

Posted on January 23, 2015 by - News

Swiss Watches the BrandScientists at the University of California, Berkeley, claim to have proved a relationship between energy and time that lets people calculate the “quantum speed limit”.
The scientists said that while the energy-time uncertainty relationship is the flip side of the Heisenberg uncertainty principle.
K Birgitta Whaley, director of the Quantum Unit at Berkeley, said: “This is the first time the energy-time uncertainty principle has been put on a rigorous basis – our arguments don’t appeal to experiment but come directly from the structure of quantum mechanics.”
She said the derivations has  implications for any measurement involving time, and certainly does for quantum computing.
Graduate student Ty Volkoff, said the uncertainty principle limits how precise your clocks can be. “In a quantum computer, it limits how fast you can go from one state to the other, so it puts limits on the clock speed of your computer.”

Scientists grab photons on silicon chips

Posted on January 12, 2015 by - News

MIT building - Wikimedia CommonsResearchers at the Massachusetts Institute of Technology (MIT) claim to have built light detectors that can register individual photons on a silicon chip.
The MIT team said they have increased the accuracy of the detectors and transferred those that work to an optical semiconductor.
The approach gives denser and larger arrays, said the MIT team with 100 times better accuracy than previous arrays.
The researchers first built a silicon optical chip using regular manufacturing processes. Then they grow a flexible film of silicon nitride on a separate silicon chip – and then the superconductor niobium nitride is despised in a pattern that can detect photons.
Gold electrodes are deposited on both ends of the detector.
Dirk Englund, a professor at MIT and part of the team, said the project was aided by IBM and NASA’s Jet Propulsion Lab.
Previous detectors only managed to pick up 0.2 percent of single photons, but MIT said detectors on its chip reached 20 percent.
We’re still a way away from quantum computing though – because MIT says 90 percent or more is needed for a working quantum circuit.

 

Quantum silicon computer gets accurate

Posted on October 13, 2014 by - News

Scientists at the University of New South WalesTwo teams working at the University of New South Wales (UNSW) claim to have an answer to problems creating quantum supercomputers.

Quantum bits – qubits – are building blocks for quantum computers and the teams now say they’ve come up with qubits that process data with an accuracy above 99 percent.

Quantum computers won’t become a reality until very low error rates are achieved, said Professor Andrew Dzurak, director of the Aussie fabrication unit at UNSW.

The teams claim to have arrived at two parallel pathways for building a quantum computer in silicon.

Dzurak said that the teams have created a so-called artificial atom that is very similar to silicon transistors used in MOSFETs. He said the experiments are the earliest using solid state devices and the first in silicon.

How far off is an effective quantum supercomputer?  The answer to that question is unclear but the next step is to create pairs of qubits, with the real thing containing thousands of millions of qubits, perhaps using thousands of millions of artificial and natural atoms.

Scientists claim quantum computing first

Posted on October 3, 2014 by - News

Quantum computingA team of researchers based in Canada says that it has a new method to generate photon pair sources that will fit into a computer chip.

Professor Roberto Morandotti of INRS-EMT  said mixed up photon pairs from devices smaller than a square millimetre, could well form the basis of quantum optical communication and computing technology.

One of the team said the process to generate polarised photons only creates particles with the same polarisation, and are then “entangled” by mixing the states. But the team said it has found a way to direcly generate cross polarised photon pairs.

The technique involves using two separate laser beams at different wavelengths and use a micro ring resonator to amplify quantum effects.

The fabrication method for the chips is compatible with electronic chips and will allow its devices to co-exist with standard integrated circuits.

The illustration above shows how cross polarised red and blue pump photons are spun into a microring resonator to generate cross polarised correlated photons, illustrated in green and yellow.