Quantum Detectors

EU-funded researchers developed an ultrasensitive detector that can sense individual light quanta in the near-infrared spectrum. Sending and receiving quantum information over long distances using single photons sets the path for more secure communications.

Produced on demand with well-defined quantum properties, single photons offer an unprecedented set of capabilities that are of revolutionary importance to modern research fields. These range from quantum information and medical diagnostics to remote sensing, photography and astronomy.

Supported partly with EU funding researchers of the project Qdet developed an innovative detector that makes complex quantum experiments easier and faster to perform. “Qdet’s new prototype system is the first to detect single photons in the near-infrared region with near-unity efficiency ultralow noise and ultrahigh time resolution” notes Dr Sander Dorenbos chief executive officer of Single Quantum project partner.

Tapping into advances in superconductivity

Project researchers built on the success of a new type of detector based on superconducting nanowires that was recently brought to market by Single Quantum. “Superconducting nanowire single-photon detectors (SNSPDs) are significantly better at photon detection efficiency compared t o their semiconducting counterparts that are still widely used in research laboratories and the industry,” notes Dorenbos.

The SNSPD is a near-infrared detector that comprises a thin and narrow film of superconducting material. It is patterned in a compact meandering nanowire form through nanofabrication processes. The nanowire is cooled well below its superconducting critical temperature and biased with a current that is close to the nanowire’s superconducting critical current.

The detection principle relies on the nanowire transition from a superconducting to a resistive state. Once a single photon is absorbed in the meandering nanowire, superconductivity is locally broken. As a result, the current is directed towards the amplification electronics and creates a voltage pulse. Superconductivity then recovers within a short time and the SNSPD is ready to detect the next photon.

To date, SNSPDs are the fastest detectors that count single photons, enabling many breakthrough applications in quantum information technologies. “Our prototype system completely outperforms state-of-the-art detectors by several orders of magnitude,” notes Dorenbos.

Optimising operation to the near-infrared

Securely transmitting quantum information over long distances requires ultrafast detectors and a quantum memory scheme that is viable for at least the transmission time. “Qdet’s single-photon detector represents an important addition to the quantum toolbox that should allow exchanging and processing information with total security,” adds Dorenbos.

The project team refined Single Quantum’s light detector to operate at 795 nm. This wavelength facilitates experimenting with quantum memory techniques that store photons in a gas of rubidium atoms since rubidium atoms emit at this exact wavelength.

Qdet’s quantum sensor operating in the near-infrared region nicely fills the company’s portfolio, which now includes high-performance detectors optimised for crucial wavelengths: 1 300 nm and 1 550 nm for optical communication research, 900 nm for quantum dots and 1 060 nm for light detection and ranging, to name a few.

Reference source: Quantum Detectors