QUantum Integrated Photonics VIP
Quantum technologies promise to revolutionize information processing through dramatic computational speed-ups and ultimate security compared with classical counterparts. As matter-based qubit systems increase in size, however, counteracting decoherence becomes challenging and places limits on how large a standalone system can be. These limitations, coupled with the many quantum computing platforms under development, have led researchers to view modular architectures, connected by a quantum network, as a promising path to large-scale quantum computing. Consequently, unleashing the full potential of quantum information processing requires mediating both communication and entanglement between distant and disparate quantum systems. The situation is not unlike cloud and high-performance computing where the linking of distributed resources has led to breathtaking advances in fields like data science and artificial intelligence.
While quantum states are extremely fragile, photons experience virtually no decoherence and are the only realistic choice to carry quantum information over long distances. There has been progress in facilitating entanglement and communication between parties using satellite-based and terrestrial free space links. However, for local and metropolitan area networks, these modes of communication are unrealistic given the need for line-of-sight access. Furthermore, the tremendous (spectral) bandwidth and low loss offered by optical fiber makes it a critical tool for interconnecting a large number of quantum resources for computing and distributed sensing.
Quantum information can be encoded in one of many attributes of a photon like polarization state, time bin, and orbital angular momentum, among others. Our focus is on frequency encoding as the frequency of a photon, relative to other photon attributes is naturally stable over optical fiber, permits straightforward measurement with high-efficiency filters and detectors, and is compatible with wavelength-division multiplexing. Our approach is based on the so-called quantum frequency processor (QFP) protocol, where electro-optic phase modulators (EOMs) and Fourier-transform pulse shapers are cascaded to realize quantum frequency gates. The QFP paradigm offers three compelling advantages. The first is that it admits massive parallelization of quantum operations in a single spatial mode (see figure above). Secondly, this architecture relies on high-speed electro-optic modulation and, therefore, has the potential to permit fast reconfiguration of quantum gates. Lastly, the frequency degree of freedom supports multilevel quantum information (qubits = two level information).
The Ultrafast Optics group at Purdue is engaged in research efforts to expand the scope of operations possible with a three-element (EOM – pulse shaper – EOM) quantum frequency processor. We are building a QFP that be will be deployed in proof-of-concept demonstrations to validate the generalization of this platform to three and higher dimensions. Along a parallel track, we are developing photonic integrated circuits (PICs) to tackle the issue of optical loss and system resolution (separation of frequencies). The anticipated outcome of this multi-year project is a low loss, chip-scale QFP capable of quantum operations with sufficient complexity to enable high-dimensional QKD (quantum key distribution) and reconfigurable entanglement swapping between independent quantum systems.
VIP Team:
Our expectation is that the work product of the VIP team will support research efforts. Consequently, a meaningful experience will require strong programming skills (Python, Matlab, other) and an interest in learning about optics and photonics. Students are not expected to have any background in quantum physics and this knowledge will be gained over the course of participation in the project. At the outset, new team members will focus on developing a FPGA-based time interval analyzer to measure coincident single-photon detection events and repeat foundational quantum optics experiments. As team members progress, they will be integrated into the project flow, which includes building benchtop optical systems to run proof-of-concept demonstrations, photonic device design and chip testing, among others. Given the multi-faceted nature of the project, students will have the flexibility to work in areas that align with their interests and abilities.
Summaries or Review Papers:
Quantum Information Processing in the Frequency Domain. Optics & Photonics News, Vol. 30 Issue 11 (2019)
Kues, M., Reimer, C., Lukens, J. M., Munro, W. J., Weiner, A. M., Moss, D. J. & Morandotti, R. Quantum optical microcombs. Nat. Photonics 13, 170–179 (2019)
Lu, H.-H., Lukens, J. M., Peters, N. A., Williams, B. P., Weiner, A. M. & Lougovski, P. Quantum interference and correlation control of frequency-bin qubits. Optica 5, 1455–1460 (2018)