Lightsynq Emerges from Stealth with $18M Series A

Lightsynq, a startup developing optical interconnect technology, has raised approximately $18 million in a Series A funding round. Founded by former Harvard quantum networking experts and research leads from Amazon Web Services Center for Quantum Networking, LightSynq is developing optical quantum interconnects that enable hardware providers to link quantum processors.

Lightsynq plans to use the funds to build prototypes of its quantum interconnects which it plans to use to help leading quantum computing companies scale to multimodule systems. Lightsynq’s quantum interconnect technology is based on color centers in diamond photonics devices, combining a leading quantum networking platform with scalable photonic fabrication. The solution, the company said, will provide a pathway to foundry-scale production of quantum interconnects, enabling more usable qubits across networks and accelerating wider industrial and commercial applications.

Lightsynq's quantum interconnect lab located at its headquarters in Boston, MA. The company uses cryogenic and optical test and measurement systems to validate the performance of its interconnect technology. Courtesy of Lightsynq.

The round saw participation from longtime collaborator Element Six, a provider of synthetic diamond material solutions. According to Element Six, the company has collaborated with Lightsynq co-founder and CEO Mihir Bhaskar’s team since 2015.

According to Lightsynq, the company’s architecture is broadly compatible with leading quantum computing modalities and leverages integrated diamond photonic circuits to link multiple limited-scale devices into a modular, full-scale quantum computer, similar to the methods used to build current high-performance computing systems. The approach uses quantum memories based on color centers in diamond, a technology that enables capabilities like heralding and in-memory computing.

One of the biggest challenges in connecting quantum computers is the network loss associated with extracting quantum information out of computing modules, Lightsynq said in a blog post. The only known solution for building loss-tolerant connections, the company said, is quantum memories.

Lightsynq’s quantum memories are created by embedding silicon atoms into diamond to form silicon vacancy color centers (SiVs) which serve as two-qubit registers that are fully controllable using microwave pulses. Lightsynq places these SiVs in optical cavities to achieve high-fidelity, high-efficiency interactions between single photons and the SiV's electron qubit. The implementation of quantum interconnects in a diamond-based photonic integrated circuit enables scaling to many parallel memory registers in a single, compact chip.

“We can perform universal quantum logic operations on our quantum memory register, enabling in-memory Bell-state measurements for entanglement swapping — a step other technologies often struggle with due to inherent inefficiencies when using linear optics for Bell-state measurements,” Lightsynq said in a blog post.

Another feature, the company said, is “heralded” memory operation, which automatically detects the successful storage of a photon in the memory, allowing the establishment of connections with high fidelity despite the large losses associated with extracting photons from a quantum computer.

Additionally, the broad acceptance bandwidth of the SiV's optical interface means the platform can work with photons from diverse quantum hardware platforms, ranging from narrow-bandwidth atoms and ions to more broadband solid-state systems, allowing them to be linked without extensive modifications.

The approach, Lightsynq said, does not require redesigns of existing quantum hardware and is designed to be compatible with quantum devices across various platforms, from atoms, ions, and photons to superconducting circuits with optical interfaces. This, the company said, allows the acceleration of the quantum industry’s timeline to commercial impact without having to pick a winning approach while the race is still underway.