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Quantum engineers from UNSW Sydney have removed a major obstacle that has stood in the way of quantum computers becoming a reality. They discovered a new technique they say will be capable of controlling millions of spin qubits—the basic units of information in a silicon quantum processor. Until now, quantum computer engineers and scientists have worked with a proof-of-concept model of quantum processors by demonstrating the control of only a handful of qubits. But with their latest research, published today in Science Advances, the team have found what they consider "the missing jigsaw piece" in the quantum computer architecture that...

The more entanglement in the so-called Hilbert space—the realm where quantum information processing can take place—the better. Previous photonic approaches were able to reach 18 qubits encoded in six entangled photons in the Hilbert space. Purdue researchers maximized entanglement with a gate using four qudits—the equivalent of 20 qubits—encoded in only two photons. In quantum communication, less is more. "Photons are expensive in the quantum sense because they're hard to generate and control, so it's ideal to pack as much information as possible into each photon," said Poolad Imany, a postdoctoral researcher in Purdue's School of Electrical and Computer Engineering....

Ultracold beryllium ions tackle 160 randomly chosen programs Using a few ultracold ions, intense lasers and some electrodes, researchers have built the first programmable quantum computer. The new system, described in a paper to be published in Nature Physics, flexed its versatility by performing 160 randomly chosen processing routines. Earlier versions of quantum computers have been largely restricted to a narrow window of specific tasks. To be more generally useful, a quantum computer should be programmable, in the same way that a classical computer must be able to run many different programs on a single piece of machinery. The new...

A research team in Japan says it has successfully demonstrated for the first time in the world in a solid-state device one of the two basic building blocks that will be needed to construct a viable quantum computer. The team has built a controlled NOT (CNOT) gate, a fundamental building block for quantum computing in the same way that a NAND gate is for classical computing. Research into quantum computers is still in its early days and experts predict it will be at least 10 years before a viable quantum computer is developed. But if they can be developed, quantum...