QKD HRDP

Quantum Key Distribution High-Rate Detector Predevelopment

IN PROGRESS

Fiber-based quantum key distribution (QKD) is limited to a few hundred kilometers, which is why satellite communication — with its minimal signal loss — is becoming increasingly important. The goal of the QKD HRDP project is to develop a high-throughput, high-efficiency single-photon detector prototype, significantly increasing the rate of secret key generation.

Context

Optical fibers in telecommunications have inherent limitations. Signals weaken with distance, and in QKD systems they cannot be amplified because, according to quantum mechanics, single photons cannot be copied. In practice, this restricts fiber-based QKD to ranges of only a few hundred kilometers.

Satellites offer an attractive alternative. In satellite links, signals travel mostly through vacuum, where losses are minimal. The atmosphere forms only a thin layer (~10 km), so its impact on transmission is relatively small. The result? Secure quantum communication over long distances becomes feasible.

However, optical links between satellites and Earth still face challenges that increase losses, including beam diffraction, pointing errors, atmospheric turbulence, and light absorption. Satellite QKD therefore relies on advanced acquisition, pointing, and tracking (APT) systems to maintain a stable, high-precision connection.

Reliable data transmission also depends on single-photon detectors that are efficient, fast, low-noise, and highly time-resolved, operating within narrow wavelength bands. Increasing detector throughput directly boosts the number of distributed keys, which can be achieved by pushing time resolution into the gigahertz range.

QKD HRDP Project Objectives:

The primary goal of the project is to develop a single-photon receiver prototype delivering high throughput (>2 GHz) and high quantum efficiency (>90%) in the 800 nm or 1550 nm wavelength bands. The system will be fully based on European technology.

Meeting these targets will remove key bottlenecks in QKD systems, significantly increasing secret key generation rates while reducing overall costs. The objective is to surpass today’s experimentally demonstrated performance levels (up to 20 kb/s).

The solution is based on SSPDs (superconducting single-photon detectors), which offer best-in-class performance among available technologies. The project builds on years of expertise in superconducting nanowires at Technische Universität München and Munich Quantum Instruments, combined with Creotech Quantum’s know-how in electronics and readout systems.

Main components of the detector prototype:

• Cryostat maintaining temperatures below 4 K, including RF cabling, sample holders, and supporting hardware

• Nanowire sensor assembly with mounting structure, fiber coupling, and electrical interfaces

• Low-noise amplifier (cryo-LNA)

• Control electronics operating at room temperature

• Complete system software, ready for end-user operation

Creotech Quantum provides the electronics, mechatronics, and software for the project.

The engineering solutions developed within the project have strong commercialization potential in quantum key distribution systems, as well as in the space and telecommunications sectors.

Consortium:

Creotech Quantum (consortium leader), Munich Quantum Instruments (MQI)

Financing:

Total project value:

799 128,07 euro

Project funding amount:

€399,734.58

Project duration:

40 months