quantum computer tagged posts

Layout of IBM’s four superconducting quantum bit device.
Credit: IBM Research

Scientists have now demonstrated for the first time developed a quantum circuit that can solve a problem that is unsolvable using any equivalent classical circuit. Conventional computers obey the laws of classical physics. They rely on the binary numbers 0 and 1. These numbers are stored and used for mathematical operations. In conventional memory units, each bit – the smallest unit of information – is represented by a microscopic dot on a microchip. Each of these dots can hold a charge that determines whether the bit is set to 1 or 0.

In a quantum computer, however, a bit can be both 0 and 1 at the same time. This is because the laws of quantum physics allow electrons to be in multiple places at one time...

An IBM cryostat wired for a 50 qubit system. Credit: IBM

IBM has announced a milestone in its race against Google and other big tech firms to build a powerful quantum computer. Dario Gil, who leads IBM’s quantum computing and artificial intelligence research division, said it’s scientists have successfully built and measured a processor prototype with 50 qubits. Gil says it’s the first time any company has built a quantum computer at this scale.

This new processor expands upon the 20 qubit architecture and will be made available in the next generation IBM Q systems. Clients will have online access to the computing power of the first IBM Q systems by the end of 2017, with a series of planned upgrades during 2018...

1. Flow Ambiguity: A Path Towards Classically Driven Blind Quantum Computation. Physical Review X, 2017; 7 (3) DOI: 10.1103/PhysRevX.7.031004
2. Illustration of an exemplary run of Protocol 1

Researchers suggest you could operate a quantum computer in the cloud without revealing your data or the program you’re running. Here’s the scenario: you have sensitive data and a problem that only a quantum computer can solve. You have no quantum devices yourself. You could buy time on a quantum computer, but you don’t want to give away your secrets. What can you do? Writing in Physical Review X on 11 July, researchers in Singapore and Australia propose a way you could use a quantum computer securely, even over the internet. The technique could hide both your data and program from the computer itself...

A cloud of cold atoms is illuminated with red signal light and blue coupling light. The light pulses are superimposed on dichroic mirrors (DM). With wave plates (WP), a polarizing beam splitter (PBS), and avalanche photodiodes (APD) the polarization of the transmitted signal light is determined. Credit: MPQ, Quantum Dynamics Division

MPQ scientists take an important step towards a logical quantum gate for photons. Commonly, a typical quantum computer is considered to be based on a network of quantum particles that serve for storing, encoding and processing quantum information. In analogy to the case of a classical computer a quantum logic gate that assigns output signals to input signals in a deterministic way would be an essential building block...