Researchers in Germany discovered a molecule that receives quantum information precisely, potentially disrupting today’s leading quantum computing technologies.
Crafted by researchers at Ulm University and NVision Quantum Technologies, this marks the first instance of such a molecule acting as a quantum bit, or qubit, that links individually via light.
Conventional computers run on binary logic by encoding information as ones and zeros through various methods such as the orientation of magnetic poles in a memory chip. Logic gates then perform calculations when specific rules are met.
A qubit is the quantum computing equivalent of a classical bit. While a classical bit stays in one of two states, a qubit can exist in a superposition of states.
This allows the two states to mix in any proportion. Quantum computers should handle information more efficiently as a result.
Single molecules have lagged behind other qubit technologies like trapped ions, superconducting circuits, and neutral atoms. Systems using those technologies have connected up to 6,100 qubits. However, they have only detected and corrected errors on a maximum of eight qubits.
Reaching practical utility requires hundreds of thousands of qubits. Linking small quantum units together with light will likely control these errors.
Before this study, researchers demonstrated reading out information about electron or nuclear spin in single molecule qubits using laser light. Individual molecular qubits could not be addressed previously because scientists had to read groups of molecules together and average their values.
The Ulm-based researchers designed a molecule called di([1,1′-biphenyl]-4-yl)carbene that provides four properties needed for an individually addressable qubit. When researchers shine a laser on it for information readout, it fluoresces only when its electrons are in one of three spin states.
Those spin states remain stable long enough for quantum computation. The molecule also fluoresces brightly enough to be read, and its color is stable enough to enable quantum entanglement.
Using a precursor housed inside a di([1,1′-biphenyl]-4-yl)methanone crystal, the team successfully produced the molecules directly.
David Awschalom from the University of Chicago described this as a high-quality molecular qubit architecture. He stated that it enables a spin–photon interface at the single-molecule level.
Awschalom noted that this development helps integrate molecular qubits with scalable optical communication platforms. Danna Freedman from the Massachusetts Institute of Technology called demonstrating single-molecule addressability and controlling its spin a huge step for the field.
NVision plans to develop molecular qubits to serve in an architecture called photonic integrated quantum circuits. Light will interact with electron spins to connect qubits, while nuclear spins serve as long-lived memories.
Ilai Schwartz, chief technology officer at NVision, explained the manufacturing route. We can tune its properties with synthetic chemistry and deposit it as a thin film on photonic integrated circuits made with existing foundry processes,
Schwartz said.
Schwartz added that this opens a manufacturable route towards large-scale quantum computers. The next step involves putting these molecules onto photonic chips with partner HyperLight.
