Temporal Multimode Transformations for Quantum Information Science

Quantum information science and technology (QIST) is a rapidly evolving field of interdisciplinary research that aims to harness the behavior of quantum systems to enable new capabilities for a range of applications including computation, communications, and sensing. A variety of physical systems are being explored for their potential to encode and manipulate quantum bits (qubits), each of which presents different advantages and challenges.

Within QIST, light plays an important role in the transport and extraction of quantum information. To date most approaches to encoding quantum information in light fields has focused on polarization and spatial profile of light beams, which are not compatible with optical fiber networks that will form the backbone of a future quantum Internet. In this project the group will develop an experimental platform to encode quantum information in temporal modes of quantum light, where the temporal shape and color of a photon, a light ‘particle,’ carries information.

Quantum applications enabled by temporal mode encoding include linear optics quantum computing, quantum communications, sensing, and simulations. Beyond the scientific and technological impacts, this project will contribute to a quantum-ready workforce through training of graduate and undergraduate students.

This project will develop methods to control and measure pulses of light at the single-photon level and its application to perform targeted operations for quantum information applications. Common approaches to shape optical laser pulses, which employ filtering or amplification, are not compatible with quantum light. To address the temporal modes of light thus requires unitary (phase only) transformations that modify the spectral and temporal phase of the light pulses.

For quantum applications most efforts have focused on nonlinear optical means for pulse control. Here the group will use linear-optical methods with electro-optic temporal phase modulation and dispersive spectral phase. The overarching research goal is the implementation of unitary transformations on temporal modes.

The proposed approach is to realize such temporal mode transformations by the sequential application of temporal phase modulation and spectral dispersion using off-the-shelf components. To overcome challenges in timing instability that arise in the application of temporal phase using electro-optic modulators, the radio-frequency driving field will be directly generated from the optical pulses that generate the single photons to be manipulated.

To verify that the targeted temporal mode transformations are experimentally implemented, an approach to characterize the transformations – a technique known as quantum process tomography – based upon spectral interferometry will be developed.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.