Delft develop maser-on-a-chip for quantum computer




Scientists from Delft have developed a small and efficient maser-on-a-chip that performs stable. The on-chip-maser is based on Josephson junctions and can serve, inter alia, in the control of qubits in a quantum computer.

Microwaves play a major role in research on quantum computers because they do not disrupt the quantum state. Scientists use them to read quantum information and error corrections to extend the life of qubits. Many sources of microwaves are expensive and inefficient, and researchers QuTech sought therefore an alternative maser, or microwave amplification by stimulated emission of radiation. They found it in the form of a link of a Josephson junction having a superconducting micro cavity.

“Quantum chips operate at a very low temperature. All equipment to check for example qubits is outside that arrangement and warm. The generation of signals to the chips far is therefore not efficient,” Julia Cramer QuTech submit to Tweakers out. The on-chip maser is small, does not heat and operates at low temperatures. “You can put them beside the qubits.”

The junction is based on an effect that Brian Josephson discovered in the seventies; between superconductors which are interrupted by a weak insulator, charge carriers can tunnel. This effect can be used to convert a voltage at specific frequencies, such as those for micro waves.

By now DC voltage for application to the Josephson-junction, can generate the QuTech researchers micro waves that resonate in the micro-cavity. By the chip to be cooled down to temperatures of up to less than 1 kelvin, radiate the microwaves from the output of the small cavity.

The advantage of the chip is formed so that the maser can be readily controlled and that there are modifications to by entering his by adjusting the design of the junction. Thus, the Delft researchers now want Josephson junctions based on nanowires designs that can send out short pulses. This allows them, in theory, check multiple qubits. In addition, future chips can operate with even smaller intensity fluctuations.

“It lets you check qubits more precisely, which is important for quantum computation”, says Cramer. A qubit is a continuous system. If you can not control very precisely, small errors occur. That is a single qubit a problem, but it builds up as there are more qubits.

The research was led by Leo Kouwenhoven and include conducted by Maja Cassidy. It was held at QuTech and the Kavli Institute of Nanoscience at Delft University of Technology and include sponsored by Microsoft.

The researchers publish their work under the heading Demonstration of an AC Josephson junction laser in the journal Science.



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