A faster method for reading quantum memory



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Faster method for reading quantum memory

The speed at which the two states of the qubit separate is much faster when two microwave probes are probed. Credit: Aalto University

The potential computer revolution long promised by quantum computers is based on their strange property called superposition. That is, qubits can take both logical states 0 and 1 simultaneously, in addition to any intermediate value. By mastering the superimpositions of the entire quantum memory, quantum computers can quickly solve problems that would require too much computing time from ordinary computers simply working with 0s and 1s.

However, qubits are sensitive and currently store quantum information less than a millisecond at a time, even when they are frozen at cooler temperatures 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 possible, allowing the least possible errors.

Joni Ikonen, Ph.D. student at Aalto University, has devised a new method to do it so far, the method used to read the information of a qubit was to apply a short microwave pulse to the superconducting circuit containing the qubit, and then to measure the reflected microwave frequency. After 300 nanoseconds, the state of the qubit can be deduced from the behavior of the reflected signal.

The new method simultaneously applies an extra microwave pulse to the qubit itself, as well as to the circuit connected to the qubit. Using two pulses instead of one, the Aalto team was able to make sure that the reflected pulses reveal the qubit states much faster than when they were applying a only impulse.

By using two separate microwaves, the two states of the qubit can be separated more quickly. Credit: Aalto University

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

"We were able to finish reading in 300 nanoseconds during our first experiments, but we believe that passing below 100 nanoseconds is imminent," says Joni Ikonen.

By improving the speed and accuracy of information extracted from qubits, scientists may be able to get closer to realizing the promise of a useful quantum calculation.

"It's an incredible result of putting order in slippery qubits. I hope this will help the community to achieve quantum supremacy and error correction in the future, the path to a quantum computer of practical value, "says Dr. Möttönen, who oversaw work with Dr. Jan Goetz.

The research is published in Letters of physical examination.


Explore further:
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More information:
Letters of physical examination (2019). DOI: 10.1103 / PhysRevLett.122.080503

Journal reference:
Letters of physical examination

Provided by:
Aalto University

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