Graphene bolometer will accelerate the development of quantum systems

Graphene bolometer will accelerate the development of quantum systems


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Evgeny Kuryshev | 31.10.2020

Graphene bolometer will accelerate the development of quantum systems

Finnish physicists from the Aalto University Low Temperature Laboratory presented a new
supersensitive detector
to measure energy. The device is suitable for use in quantum computers when reading the states of qubits. This requires high speed and
the sensitivity of measurements, which were achieved due to the use of graphene as an active element of the detector. Details of the scientific work are published in the journal Nature.

In the vast majority of modern quantum computers, the energy state of a qubit is determined by measuring its voltage. Due to the technical difficulty in implementing such
Measurements in practice, this greatly limits the modernization and scalability of such systems. There are other disadvantages of this approach, among which, in particular, quantum noise,
created by massive amplifying elements – this leads to an increase in the number of errors when reading the state of the qubit. In addition, the amplifier stage requires a lot of power to function.
In connection with the search for an alternative, scientists have long considered the possibility of using a bolometer for these purposes – a device invented in its original form back in 1878 and intended
for registration of electromagnetic radiation and measurement of its power. The principle of operation of the device is very simple – when radiation hits the temperature-sensitive element of the bolometer, it heats up, which
leads to a change in the electrical resistance of the heat sink. By measuring the latter, the energy absorbed by the device is assessed.

But the main problem was that bolometer options based on other materials, for example, an alloy of gold and palladium, did not allow achieving the required for work in quantum computers
speed and sensitivity level of measurements. Therefore, the scientists decided to try graphene, which has a very low heat capacity, which was the key to solving the problem. Due to this property
graphene, even very small changes in the energy emitted by a qubit lead to a rapid change in temperature and resistance of the new bolometer. Finnish-designed device is capable of
carry out the necessary measurements in just a few hundred nanoseconds, which is more than enough for use in modern quantum systems. The minimum recorded during scientific
experiments time – 200 nanoseconds. By the way, the dimensions of the active part of the new detector correspond to the scale of the bacterial world, so on one quantum chip it is possible to fit a whole array of such
bolometers.

Scientists acknowledge that the technology still needs further refinement and continue to work to increase its sensitivity. But it is already clear that in the future the use of graphene
bolometers should increase the speed and accuracy of quantum systems. Ultimately, this could usher in the era of the applied use of quantum computers.

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