A variety of materials continue to compete for preeminence in the race toward a quantum computer. It is expected that a future quantum computing (QC) design would combine multiple qubit technologies under the umbrella of a universal quantum interconnect. Thus, an overarching challenge is how to interface quantum information between various qubit materials (e.g., Si:P and Ca+ qubits), often held at diverse physical environments and spatial locations. Photonic qubits are the natural choice: they suffer from virtually no decoherence, are readily controlled, and operate equally-well at any temperature. Moreover, QC can be realized on photonic qubits directly. Unfortunately, dissimilar material qubits require different frequency photons to couple qubits in and out, and existing photonic qubit technologies are not designed to process photons distinguishable in frequency.
Here we propose an entirely new experimental photonic qubit interface which will enable quantum connections between common material qubits such as ions or atoms. Rather than encoding information in space or polarization, each photonic qubit consists of two frequency modes, the specific values of which can be chosen to match disparate atomic levels in different qubit types. Our approach eliminates the need for complex conventional interferometers in favor of standard telecommunications components, and upon successful completion, ORNL will have a new qubit interface technology eliminating major drawbacks of past attempts and furnishing a novel optical platform for material-based qubit networks.
Develop a technology enabling exchange of quantum information between dissimilar matter qubits
• Develop a protocol to mediate operations between remote qubits using single photons of different frequencies
• Experimentally demonstrate high-fidelity quantum operations on photons of dissimilar frequencies
• Utilize the technology as a part of the future material qubit testbed and quantum internet