Another step forward on universal quantum computer

August 13, 2018, Yokohama National University
Nitrogen-vacancy (NV) center in diamond with two crossed wires for holonomic quantum gates over the geometric spin qubit with a polarized microwave. Credit: Yokohama National University

Researchers have demonstrated holonomic quantum gates under zero-magnetic field at room temperature, which could enable the realization of fast and fault-tolerant universal quantum computers.

A quantum is a theoretical machine with the potential to solve complex problems much faster than conventional computers. Researchers are currently working on the next step in quantum computing—building a universal quantum computer.

The paper, published in the journal Nature Communications, reports experimental demonstration of non-adiabatic and non-abelian holonomic quantum gates over a geometric spin qubit on an electron or nitrogen nucleus, which paves the way to realizing a universal quantum computer.

The geometric phase is currently a key issue in quantum physics. A holonomic quantum gate purely manipulating the geometric phase in the degenerate ground state system is believed to be an ideal way to build a fault-tolerant universal quantum computer. The geometric phase gate or holonomic quantum gate has been experimentally demonstrated in several quantum systems, including nitrogen-vacancy (NV) centers in diamond. However, previous experiments required microwaves or light waves to manipulate the non-degenerate subspace, leading to the degradation of gate fidelity due to unwanted interference of the dynamic phase.

"To avoid unwanted interference, we used a degenerate subspace of the triplet spin qutrit to form an ideal logical qubit, which we call a geometric spin qubit, in an NV center. This method facilitated fast and precise geometric at a temperature below 10 K, and the gate fidelity was limited by radiative relaxation," says corresponding author Professor Hideo Kosaka of Yokohama National University. "Based on this method, in combination with polarized microwaves, we succeeded in manipulation of the geometric phase in an NV center in diamond under a zero-magnetic field at room temperature."

The group also demonstrated a two-qubit holonomic gate to show universality by manipulating electron-nucleus entanglement. The scheme renders a purely holonomic gate without requiring an energy gap, which would have induced dynamic interference to degrade the gate fidelity, and thus enables fast, precise control over long-lived quantum memory, a step toward realizing quantum repeaters interfacing between universal computers and secure communication networks.

Explore further: Experimentally demonstrated a toffoli gate in a semiconductor three-qubit system

More information: Kodai Nagata et al, Universal holonomic quantum gates over geometric spin qubits with polarised microwaves, Nature Communications (2018). DOI: 10.1038/s41467-018-05664-w

Related Stories

Simple is beautiful in quantum computing

November 15, 2017

Quantum computing could solve problems impossible for today's supercomputers. The challenge for this new form of computing is processing the quantum bits (qubits) that represent data. A qubit can be made by controlling the ...

Researchers successfully simulate a 64-qubit circuit

June 26, 2018

Quantum computers are based on the principles of quantum mechanics. Compared with classical bits, qubits can be at the superposition between zero and one, so a quantum computer composed of qubits can calculate and store more ...

New silicon structure opens the gate to quantum computers

December 12, 2017

In a major step toward making a quantum computer using everyday materials, a team led by researchers at Princeton University has constructed a key piece of silicon hardware capable of controlling quantum behavior between ...

Recommended for you

Bursting bubbles launch bacteria from water to air

November 15, 2018

Wherever there's water, there's bound to be bubbles floating at the surface. From standing puddles, lakes, and streams, to swimming pools, hot tubs, public fountains, and toilets, bubbles are ubiquitous, indoors and out.

Terahertz laser pulses amplify optical phonons in solids

November 15, 2018

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg/Germany presents evidence of the amplification of optical phonons ...

Designer emulsions

November 15, 2018

ETH material researchers are developing a method with which they can coat droplets with controlled interfacial composition and coverage on demand in an emulsion in order to stabilise them. In doing so they are fulfilling ...

Quantum science turns social

November 15, 2018

Researchers in a lab at Aarhus University have developed a versatile remote gaming interface that allowed external experts as well as hundreds of citizen scientists all over the world to optimize a quantum gas experiment ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

DonGateley
not rated yet Aug 17, 2018
I can't believe this is the first comment. This is HUGE folks in some terrifying ways. Unless there are down sides that aren't described or they cannot be easily connected to adjacent Qbits to form registers (or other structures) of them, then the (unstable) world will soon be aswarm with such computers. First thing to do will be to crack all known cryptographic methods. What's next is up to your imagination.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.