A faster method to read quantum memory

Faster method to read quantum memory
The speed at which the two states of the qubit separates is much faster when probed with two microwaves Credit: Aalto University

The potential computing revolution that quantum computers have long promised is based on their weird property called superposition. Namely, qubits can take both logical states 0 and 1 simultaneously, on top of any value in between. By mastering superpositions of the whole quantum memory, quantum computers can quickly solve problems that would require too much computing time from regular computers working with simply 0s and 1s.

However, qubits are sensitive, and currently hold for less than a millisecond at a time, even when kept frozen at temperatures colder than the dark side of the moon. To extract any useful information, the method that reads information from qubits must take the least amount of time as possible, allowing as few errors as possible.

Joni Ikonen, a Ph.D. student at Aalto University, has developed a new method that helps do just that. Until now, the method used to read information from a was to apply a short microwave to the superconducting circuit containing the qubit and then measure the reflected microwave. After 300 nanoseconds, the state of the qubit can be deduced from the behavior of the reflected signal.

The new method applies an extra microwave pulse at the same time to the qubit itself, as well as to the circuit attached to the qubit. By using two pulses instead of one, the team at Aalto was able to make the reflected pulse reveal qubit states substantially faster than when they only applied a single pulse.

Faster method to read quantum memory
By using two separate microwaves, the two states of the qubit can be separated faster Credit: Aalto University

Caption: The two states, here represented by red and blue arrows, separate faster and can be read quicker when the system is pulsed with two microwaves

'We were able to complete the readout in 300 nanoseconds in our first experiments, but we think that going below 100 nanoseconds is just around the corner,' says Joni Ikonen.

By improving the speed and accuracy of the information retrieved from qubits, scientists may be able to move closer to realising the promise of useful .

'This is an amazing result in getting the slippery qubits in order. I hope that it will help the community in the future to reach quantum supremacy and , the path to a quantum computer of practical value,' says Dr. Möttönen, who co-supervised the work with Dr. Jan Goetz.

The research is published in Physical Review Letters.


Explore further

Quantifying how much quantum information can be eavesdropped

More information: Physical Review Letters (2019). DOI: 10.1103/PhysRevLett.122.080503
Journal information: Physical Review Letters

Provided by Aalto University
Citation: A faster method to read quantum memory (2019, February 25) retrieved 19 June 2019 from https://phys.org/news/2019-02-faster-method-quantum-memory.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
322 shares

Feedback to editors

User comments

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