IQM researchers have collaborated with Aalto University and VTT Technical Research Centre of Finland to demonstrate a cryogenic microwave source with unprecedented potential for quantum computers. The results are published in Nature Electronics.
At IQM, our core products are technology and solutions based on superconducting quantum computing. A large part of the work consists of developing and scaling quantum hardware. An important aspect of a functional quantum computer is the control electronics for the manipulation and reading out the quantum states. In superconducting quantum computing, the control is performed with microwave signals. While microwave technology is in principle well established – for example used commonly in everyday mobile phone communication – performing high-quality quantum operations preserving the key ingredient, the quantum coherence, requires high-end microwave instrumentation with ultra-high signal quality. Today, this is achieved with state-of-art microwave instrumentation residing at room temperature as opposed to the quantum processor located in a refrigerator and cooled down close to the temperature close to the absolute zero, -273 C. Arranging the connectivity to pass the signals between the two is a further challenge as such. With today’s intermediate-scale quantum computers, such as those provided as IQM’s first commercial systems [ Link 1 ], [ Link 2 ] the approach is still functional. However, looking beyond, it is tempting to compact the quantum computer by integrating control electronics in the cryostat.
IQM is a part of collaboration that has recently published results from a low-temperature integrated microwave source studied for the purposes of quantum control. Integrated control electronics operating in the same environment as the quantum processor could in principle solve many issues in the scaled-up quantum computer like decreasing the required cryostat volume and thermal loading consumed by the cabling to the room temperature. It could also provide short signal delays between the control and the processor, useful in quantum error correction. However, there are substantial challenges in such integration. At the lowest temperatures of the cryostat the cooling capacity is orders of magnitude lower than the power consumption of conventional electronics whence specialized solutions are needed. Also, the signal quality needs to comply with the stringent requirements of quantum computing. The published research demonstrates a microwave oscillator based on the Josephson effect. The oscillator operates as a continuous-wave microwave source that as such is not yet useful for the qubit control. Yet, an oscillator is a key component of several possible implementations acting as a reference clock, or for carrier signal generation for different signal shaping techniques. The key published results include modeling techniques useful for engineering such sources to optimize basic parameters like the operating frequency and amplitude, and to optimize the power generation efficiency. Importantly, the collaboration demonstrated that the signal quality and amplitude are sufficient for controlling state-of-art superconducting qubits. Also, power consumption was shown to be very low – thanks to the high power-generation efficiency – and thus compliant with the cooling systems used in quantum computing.
The work was pursued in collaboration with Aalto University and VTT Technical Research Centre of Finland. The results are published in Nature Electronics.
