What would a programmable quantum chip actually do?

In a programmable architecture, a researcher could retune sources, reroute photons, and reconfigure detectors after fabrication. The authors list quantum neural networks and distributed quantum computing among the possible applications. They argue programmable quantum circuitry will play a pivotal role in moving quantum optics from proof-of-concept demonstrations to deployable technology.

The team flags one stubborn obstacle: multifunctionality. To run several tasks at once, a system must reconfigure multiple components simultaneously — for example, changing a light source's wavelength and polarization while steering photons to different detectors.

How could 2D materials help?

The review identifies three programmable building blocks: tunable quantum light sources, dynamic modulators, and reconfigurable detectors. For each, the authors point to van der Waals crystals — layered solids held together by weak intermolecular forces — as a promising platform. While most current quantum light sources rely on nonlinear processes that split photons into entangled pairs, the authors argue that single-photon emitters hosted in van der Waals crystals could offer a more controllable alternative.

These crystals can be adjusted by stacking or twisting their atomic layers. Researchers have already built tiny electrically driven mechanical systems, known as MEMS, that can tune such crystals and other on-chip components.

"It's remarkable how much control is possible simply by changing how these ultrathin materials are stacked on top of one another," Crozier said.

The team also describes how 2D materials could create exotic light states — quantum vortices and vector beams — that encode information across multiple dimensions rather than a single frequency or polarization. Those states would significantly increase the bandwidth of photonic circuits.

What still needs to work?

The authors are candid about the limits. Van der Waals sources do not yet match the brightness, photon purity, or coherence of established emitters such as quantum dots and color centers, they write, and more work is needed.

For modulators, no single material platform currently satisfies the three criteria the authors consider essential: efficient energy coupling, low-energy ultrafast switching, and scalability. They argue 2D materials could eventually meet all three.

"Two-dimensional materials are powerful and have myriad functionalities," Aharonovich said. They enable bandgap engineering, optoelectronic and nonlinear functionalities, and quantum light sources, and could in principle supply every component of a future quantum circuit, he added.

What comes next?

The roadmap raises as many questions as it answers. Whether benchmarks like source brightness, modulator switching speed, and chip-scale scalability can be met in practice remains unclear. The authors expect follow-up experiments — especially those combining MEMS with stacked 2D layers — will test whether the platform is ready for prime time.