Ongoing testing of quantum computing and quantum communications on the International Space Station (ISS) has the potential to overcome a key problem with space-based quantum communications. A key part of the tests is a unique photon detection unit, one that was designed and built by the University of Waterloo’s Institute for Quantum Computing (IQC).
The technology was funded under the Canadian Space Agency’s (CSA’s) Flights and Fieldwork for the Advancement of Science and Technology (FAST) initiative.
SpaceQ reached out to IQC’s lab faculty supervisor, Professor Thomas Jennewein, about their detector, the broader research project, and why it’s on the ISS in the first place.
SEAQUE and quantum communications
Quantum communications, in brief, uses pairs of particles (usually photons) called “qubits”. Qubits exist in a state of “superposition”, representing neither a binary “0” nor “1” but multiple combinations of both simultaneously. They’re used in research into specialized quantum computation. They’re also used for secure communication: the nature of quantum mechanics means that any “man in the middle” hack on qubit-based communications would cause them to decohere and make the intrusion obvious.
In addition, these qubits can be “entangled”, where pairs of qubits are generated with linked quantum states. If the state of one is changed, the other instantaneously changes, even if separated by extremely long distances. This could theoretically be used for high-speed communications, even over long distances, though development of this technology is still very early and much is yet to be discovered and understood.
SEAQUE (Space Entanglement and Annealing QUantum Experiment) is a research project to better understand how all this works, and how it can be used in space. Jennewein said that it “aims to test quantum communication technologies in the space environment”, and is a combined effort between “research colleagues at University of Illinois / Urbana Champaign and NASA JPL”, as well as ADVL, Boeing, the National University of Singapore and the IQC at the University of Waterloo.
SEAQUE was transported to the station aboard a SpaceX Cargo Dragon as part of the CRS-31 commercial resupply mission, which launched in early November of 2024.
According to NASA, SEAQUE is part of the MISSE-20 platform. MISSE (Materials International Space Station Experiment) is a series of experiments performed outside of the International Space Station, mounted externally on the Station’s hull. This exposes the experiments inside the MISSE to the harsh conditions of space, including extreme radiation, helping scientists to better understand how and whether a technology needs to be “space-hardened” before being deployed.
Jennewein said that SEAQUE itself “tests quantum technologies (photon sources, photon detection and laser for detector ‘radiation healing’) [that are incorporated] into one unit.” In particular, the SEAQUE experiment is intended “to verify the quantum entanglement of the photon pairs upon continued operation in space”.
Jennewein added that these technologies “could be used in future quantum network missions, and be useful for quantum transmitter or quantum receiver nodes.” As qubits can be fragile, with decoherence always being a key consideration, understanding how they stand up to space could become critical for refining and deploying this technology in the future.
The provided photon detector
One of IQC’s areas of expertise is quantum optics–technology “using single quanta of light” (photons) in Jennewein’s words, and their contribution to SEAQUE leverages that expertise.
The device they provided for the SEAQUE experiment is a detector of these “single quanta of light”, though it is a fair bit more complex than that. Jennewein explained that it actually has “4 photon detector channels, which are counted (per second)”, and that it will “search for coincident detections within a time window of about 1 nano second.” Each channel is connected to the optical unit by optical fiber, with each “required to characterize and monitor the entangled photon source.”
It has “a small form factor and low power consumption”, he said, “so that it can fit into the size-mass-power requirements of a satellite mission”. This makes sense; it’s based on the photon detectors they built and tested for the QEYSSat mission, which is also studying space-based quantum communications.
This specific project, he said, was “lead by MSc student Joanna Krynski, with support from various members including Paul Godin, Nigar Sultana and others.” It is a custom unit “based on high-quality single photon detectors provided by Excelitas”, as well as “a simple electronics for coincidence counting provided by [Austria’s] DotFast”.
Jennewein also mentioned a key aspect of the SEAQUE project: its laser-based “self-healing”. NASA said that space radiation will eventually degrade the detectors, which will initially appear as ”‘dark counts” in a detector’s output and eventually generate so much noise that the detector becomes useless. This may necessitate regular replacement of the detectors, which would be difficult-to-impossible in space.
SEAQUE uses the laser’s heat to periodically “bubble away” (or “anneal”) the radiation-induced damage, repairing the surface of the detector and preventing the “dark counts” and noise. If it works, it will keep the detector working and the system functional, and Jennewein said that the detector was specifically designed “to support testing the detector annealing process”.
Moving detectors to space
Interestingly enough, prior to getting involved with SEAQUE, this testing was intended to be done on the ground. Their initial contribution, he explained, was supported by a CSA-FAST grant, which was “aimed at testing next generation quantum technologies under space environment conditions.” Their initial proposal “planned for radiation tests at radiation facilities such as TRIUMF”, he said, and “several of the partners had provided their support for the project.”
Once they received the grant, Jennewein said, “the SEAQUE mission became a possibility”, prompting his team at IQC to “change focus to focus to implement these tests on an actual space experiment.” While working with TRIUMF and other partners would have been helpful, Jennewein said that “it is always better to study the performance of a technology under the correct conditions, rather than a simulated experiment on the ground.”
The testing, according to Jennewein, has been taking place since the CRS-31 mission reached the ISS last November. “The system was launched in early November”, he said, and “has been operational since that time, generat[ing] several experimental runs.”
Going forward, Jennewein said that future communication missions “will benefit from the insights learned during the SEAQUE mission”. He pointed to the laser annealing of the detectors, in particular, as “a very important approach to mitigate the radiation damage impact on these detector devices.”
As for IQC, they’re refocusing on their other big project: the QEYSSat mission, a microsatellite built by Honeywell and the IQC that will “test quantum communication between ground and space”. The CSA’s resources on the mission say that QEYSSat is “in development”, launching sometime in 2026, and will last for at least a year. It also says that Honeywell will “build, test, deliver, launch, [and] commission” the satellite, while IQC will “lead QEYSSat scientific support, QKD application and demonstration development, and quantum source development for the ground station.”
