UK funds $400 million for quantum computers and has promising trapped ion results for a scalable system

A consortium of academic and industrial partners led by Oxford University will deliver quantum technologies including building a fully-functional prototype quantum computer. The Oxford-led Hub for Networked Quantum Information Technologies (NQIT) will look to combine state of the art systems for controlling particles of light (photons) together with devices that control matter at the atomic level to develop technologies for the future of communications and computing.

NQIT is one of four Quantum Technology Hubs that will be funded by the Engineering and Physical Sciences Research Council (EPSRC) from the £270 million (about $400 million) investment in the UK National Quantum Technologies Programme announced by the Chancellor, George Osborne in his Autumn Statement of 2013.

The Oxford-led Hub will use a novel network architecture, where building blocks such as trapped ions, superconducting circuits, or electron spins in solids, are linked up by photonic quantum interconnects.

Oxford researchers published promising trapped ion quantum results recently.

The researchers trapped a Ca+ ion on a sapphire substrate using an electric field—modifying the field allowed for representing “0” or “1” qubit states. In so doing, the researchers found that they could achieve a coherence time of up to 50 seconds—a record for a non-shielded atomic-ion. researchers then used laser pumping techniques to prepare the ion’s electron to a ground state, then applied optical excitation to read the qubit state. The team ran this same procedure 150,000 and reported an average error rate of just 0.07 percent—clearly much better than the 1 percent benchmark. The then applied 3.2-gigahertz microwave pulses to cause the qubits to act as logic gates—they report near perfect accuracy. They followed that up by generating a long sequence of logic gate operations which ran with an error rate of just 1×10−6—again, much better than the benchmark.

The results by the team suggest that trapped calcium ions may indeed prove to be a suitable means for representing qubits in a quantum computer, though a lot more research is yet to come—integrating all the functionalities in a single setup, for example.

Qubits made of a trapped 43Ca+ ion. RF and dc electrodes provide a trapping field for the ions, which are cooled by laser beams (blue) to microkelvin temperatures. A combination of laser pumping and microwave signals can deterministically prepare the qubit in a |0〉 or |1〉 state, and the state can be read out by monitoring its fluorescence (only |1〉 states result in the fluorescence, similar to that shown in the inset). Further logical gate operations can be carried out by applying various combinations of microwave pulses. The scheme yields preparation and readout errors of less than 0.07% and logic-gate errors of less than 10-6. Credit: APS/Alan Stonebrak

Physical Review Letters – High-Fidelity Preparation, Gates, Memory, and Readout of a Trapped-Ion Quantum Bit

Abstract

They implement all single-qubit operations with fidelities significantly above the minimum threshold required for fault-tolerant quantum computing, using a trapped-ion qubit stored in hyperfine “atomic clock” states of 43Caþ. We measure a combined qubit state preparation and single-shot readout fidelity of 99.93%, a memory coherence time of T*2 = 50 sec, and an average single-qubit gate fidelity of 99.9999%. These results are achieved in a room-temperature microfabricated surface trap, without the use of magnetic field shielding or dynamic decoupling techniques to overcome technical noise.

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