A team of researchers from the University of Ottawa’s Nexus for Quantum Technologies Institute (NexQT) has developed a groundbreaking technique for evaluating the performance of quantum circuits. Led by Dr. Francesco Di Colandrea under the supervision of Professor Ebrahim Karimi, the team’s innovative method was recently published in the journal npj Quantum Information, marking a significant advancement in the field of quantum computing. In the rapidly evolving landscape of quantum technologies, ensuring the functionality and reliability of quantum devices is crucial for their efficient integration into circuits and computers, impacting both fundamental studies and practical applications.
Characterization plays a pivotal role in determining if a device operates as expected, particularly when anomalies or errors arise. Addressing these issues is essential for advancing the development of future quantum technologies. Traditionally, scientists have relied on Quantum Process Tomography (QPT), which involves a large number of “projective measurements” to fully reconstruct a device’s operations. However, the scalability of QPT with the dimensionality of operations poses significant experimental and computational challenges, especially for high-dimensional quantum information processors.
The University of Ottawa research team has introduced an optimized technique called Fourier Quantum Process Tomography (FQPT), which enables the complete characterization of quantum operations with a minimal number of measurements. By utilizing the Fourier transform within two different mathematical spaces, FQPT enhances the information extracted from single measurements, drastically reducing the number of necessary measurements. For processes with dimensions 2d, only seven measurements are required, showcasing the efficiency of this novel technique.
To validate their technique, the researchers conducted a photonic experiment using optical polarisation to encode a qubit. Leveraging state-of-the-art liquid-crystal technology, the quantum process was implemented as a complex space-dependent polarisation transformation. This experiment demonstrated the method’s flexibility and robustness, emphasizing its potential for real-world applications. Francesco Di Colandrea, a postdoctoral fellow at the University of Ottawa, highlighted the importance of experimental validation in ensuring the technique’s resilience to noise and achieving high-fidelity reconstructions in realistic scenarios.
The researchers are now actively working on expanding FQPT to arbitrary quantum operations, including non-Hermitian and higher-dimensional implementations. Additionally, they are exploring the integration of AI techniques to enhance accuracy and reduce the number of measurements required. This new technique represents a promising avenue for further advancements in quantum technology, with the potential to revolutionize the field of quantum computing. The innovative approach developed by the University of Ottawa team showcases the power of collaboration and innovation in driving progress in quantum technologies.