The Future of Quantum Computing: Bolometers Revolutionizing Qubit Measurement

In the quest for ever-higher qubit counts in near-term quantum computers, engineers face the challenge of refining how qubits are measured. Traditionally, parametric amplifiers have been used for this purpose, amplifying weak signals from the qubits for readout. However, this amplification process introduces unwanted noise and can lead to decoherence of the qubits without additional large components. Moreover, as qubit counts increase, the bulky size of the amplification chain becomes a technical hurdle in size-limited refrigerators.

Aalto University’s research group Quantum Computing and Devices (QCD) has introduced a revolutionary solution to this problem. They have demonstrated in a Nature Electronics paper that thermal bolometers can serve as ultrasensitive detectors for qubit measurements, accurate enough for single-shot readout. Unlike traditional amplifiers, bolometers measure power or photon number, evading the limitations of the Heisenberg uncertainty principle. This allows bolometers to detect microwave photons emitted from the qubit with minimal disturbance. The small form factor of bolometers, approximately 100 times smaller than amplifiers, makes them an attractive alternative for qubit measurement in the future of quantum computing.

Bolometers offer several key advantages over parametric amplifiers. They eliminate quantum noise introduced by the Heisenberg uncertainty principle, providing accurate measurements without additional noise. Bolometers are also significantly smaller in size, allowing for more compact and scalable quantum computing systems. Aalto University Professor Mikko Möttönen emphasizes the importance of evaluating the footprint of each component for massive qubit scale-up, highlighting the potential of nanobolometers as an alternative to traditional amplifiers.

The QCD group’s experiments have shown promising results in achieving high fidelity qubit readout with bolometers. They obtained a single-shot fidelity of 61.8% with a readout duration of 14 microseconds, which increases to 92.7% when accounting for the qubit’s energy relaxation time. With minor modifications such as using graphene as a bolometer material and removing unnecessary components, the team expects to achieve a single-shot fidelity close to 99.9% in just 200 nanoseconds. This improvement not only enhances readout fidelity but also simplifies the measurement device, making it more suitable for scaling up to higher qubit counts.

The Future of Quantum Computing with Bolometers

The potential of bolometers in revolutionizing qubit measurement for quantum computing is evident. The QCD research group’s groundbreaking work showcases the accuracy and efficiency of bolometers in single-shot qubit readout. By leveraging the unique capabilities of bolometric energy sensing, researchers can overcome the limitations of traditional amplifiers and pave the way for future advancements in quantum computing technology. With ongoing research and development, bolometers have the potential to play a crucial role in unlocking the full potential of quantum computing in the years to come.