The quest for larger qubit counts in near-term quantum computers has sparked a need for innovative engineering solutions. Traditional parametric amplifiers have been the go-to devices for measuring qubits, amplifying weak signals for readout. However, the noise generated by this amplification process can lead to decoherence and hinder accurate measurements, particularly as qubit counts increase. This is where the Aalto University research group Quantum Computing and Devices (QCD) steps in with a groundbreaking alternative.
In a recent publication in Nature Electronics, the QCD research group unveiled the potential of using thermal bolometers as ultra-sensitive detectors for single-shot qubit readout. Unlike parametric amplifiers, bolometers measure power or photon number, bypassing the limitations imposed by the Heisenberg uncertainty principle. By subtly sensing microwave photons emitted from the qubit, bolometers provide accurate measurements without introducing quantum noise. In addition, the compact size of bolometers makes them a highly appealing choice for qubit readout, being approximately 100 times smaller than traditional amplifiers.
Professor Mikko Mӧttӧnen, head of the QCD research group, emphasizes the importance of component footprint evaluation for future quantum computing scalability. The nanobolometers developed by the group offer significant advantages over conventional amplifiers. These bolometers are not only accurate for single-shot readout but also consume 10,000 times less power, making them a sustainable and efficient choice for quantum measurements. Furthermore, their compact size allows for integration within extremely small devices, with the temperature-sensitive part fitting inside a single bacterium.
The QCD group’s experiments demonstrate impressive single-shot fidelity results, with a measured accuracy of 61.8% and the potential for further improvement. By optimizing the bolometer material, such as switching from metal to graphene with lower heat capacity, faster energy detection can be achieved. This, combined with the removal of unnecessary components in the measurement setup, can lead to significantly higher fidelity rates, approaching the desired 99.9% in a fraction of the time.
Before showcasing the high single-shot readout fidelity of bolometers, the QCD group had already proven their worth in ultrasensitive microwave measurements. These groundbreaking advancements were made possible through collaboration with various research institutions and quantum technology centers, highlighting the interdisciplinary nature of quantum computing research. By leveraging the unique capabilities of bolometers, the QCD group aims to pave the way for more efficient and accurate qubit measurements, enabling the scalability of quantum systems to unprecedented levels.
The utilization of bolometers for qubit readout represents a paradigm shift in quantum computing. With their ability to overcome the limitations of traditional amplifiers and deliver superior measurement accuracy, bolometers hold immense potential for shaping the future of quantum technology. As researchers continue to explore novel applications and optimizations, the era of quantum supremacy may be closer than we think, thanks to the revolutionary advancements in qubit measurement techniques.
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