Quantum computing tagged posts

Researchers from MIT and MIT Lincoln Laboratory report an important step toward practical quantum computers, with a paper describing a prototype chip that can trap ions in an electric field and, with built-in optics, direct laser light toward each of them.

Built-in optics could enable chips that use trapped ions as quantum bits. Although quantum systems with as many as 12 qubits have been demonstrated in the lab, building quantum computers complex enough to perform useful computations will require miniaturizing qubit technology, much the way the miniaturization of transistors enabled modern computers.

Trapped ions are probably the most widely studied qubit technology, but they’ve historically required a large and complex hardware apparatus...

Multiple reflections like in a drop of paint

Inside a drop of paint, light is scattered so often that it seems impossible to demonstrate quantum effects. But despite the thousands of possible paths the light can take, researchers of the Uni of Twente now show that there are just 2 exits. Depending on the light pattern that enters the paint, 2 photons always come out through the same exit, or through different ones – as though they avoid each other.

Most of the experiments showing that light sometimes behaves like a wave and sometimes like a particle, are as simple as possible: a physics textbook example is Young’s two slit experiment. The number of possible light paths is limited, but even at this level, the experiments strongly challenge our intuition...

An artist’s rendering of the quantum Fredkin (controlled-SWAP) gate, powered by entanglement, operating on photonic qubits. Credit: Raj Patel and Geoff Pryde, Center for Quantum Dynamics, Griffith University.

The quantum circuit Fredkin gate has been experimentally realised for the first time. “Similar to building a huge wall out lots of small bricks, large quantum circuits require very many logic gates to function. However, if larger bricks are used the same wall could be built with far fewer bricks,” said Dr Patel. “We demonstrate in our experiment how one can build larger quantum circuits in a more direct way without using small logic gates.”

At present, even small and medium scale quantum computer circuits cannot be produced because of the requirement to integrate so many of these gate...

Photons are generated simultaneously in pairs, each in one of the photon streams. The detection of photons in one stream indicates the timing information of those in the other. Using this information, a proper timing control is dynamically applied to those photons so they appear at regular intervals. This new technique increases the rate of photons at the regular interval, which is extremely useful for quantum secure communication and quantum photonic computation. Credit: University of Sydney

The interdisciplinary research is set to revolutionize our ability to exchange data securely – along with advancing quantum computing, which can search large databases exponentially faster...