Quantum computers could hunt dark matter at LHC
A particle physicist is developing quantum algorithms to search for anomalies in data from the upgraded Large Hadron Collider, aiming to find signs of dark
Particle physicists are preparing for a data deluge when the Large Hadron Collider (LHC) restarts in 2030. The upgraded High-Luminosity LHC will produce about ten times more collisions than before, creating a monumental challenge to find signs of new physics buried within billions of ordinary events.
Sarah Alam Malik, a particle physicist at University College London, believes quantum technologies could provide a solution. After over a decade searching for dark matter at the LHC, she is now developing quantum algorithms to spot unusual patterns in collision data. The goal is to use these tools to probe for physics beyond the standard model, our current best theory of the universe.
The hunt for dark matter
One major motivation for this search is dark matter, which accounts for roughly a quarter of the universe's content. "We know there's something that we've dubbed dark matter, which accounts for a quarter of the universe," Malik told New Scientist. Evidence for this invisible scaffolding comes from the rotational speeds of stars within galaxies to the large-scale structure of the cosmos.
A leading candidate is a type of particle known as a weakly interacting massive particle, or WIMP. Some theories, like supersymmetry, predicted WIMPs and offered an elegant solution dubbed the "WIMP miracle" that could explain both dark matter and the surprisingly light mass of the Higgs boson. So far, dedicated searches at the LHC have not found WIMPs, prompting a shift in strategy.
A model-agnostic approach
There is now a strong push for more bottom-up, model-agnostic searches. Instead of only looking for particles predicted by specific theories like supersymmetry, physicists want to let the data guide them. Malik sees quantum computing as a potentially disruptive technology that could accelerate this process.
One technique is quantum-enhanced anomaly detection. The concept is similar to how banks use algorithms to spot fraudulent transactions by identifying deviations from normal patterns. In particle physics, algorithms would be trained on data from standard model processes. Quantum computers might then identify anomalies that diverge from the standard model with greater sensitivity.
Use quantum information
The particle collisions at the LHC are inherently quantum processes. However, when particles pass through the detectors, the information becomes classical data. A quantum system holds information about a range of possible outcomes and correlations between particles, but much of this is lost during measurement.
Malik's research aims to apply minimal classical processing to the raw detector data. The hope is that this will preserve more of the underlying quantum information. Quantum algorithms could then analyze this less-processed data to identify subtle patterns and separate event types in ways difficult for classical computers. Exploratory studies are promising, but the full extent of the quantum advantage is not yet clear.
Researchers are also investigating whether quantum sensors could extract information without fully destroying the delicate quantum states of the collisions. Malik notes this area is still in its infancy but represents an exciting possibility.
Future timelines and cosmic questions
Quantum computing is expected to mature over the next decade, potentially aligning with the 2030 restart of the High-Luminosity LHC. Malik hopes this confluence will allow physicists to use quantum tools fully when the enormous new dataset arrives.
The search remains open-ended. Dark matter might not be a single new particle. Alternative explanations, like modified gravity, exist, though particle-based dark matter remains the leading contender as it explains a broader range of cosmic observations.
Even if a promising particle is found at a collider, confirming it as the cosmic dark matter would be a separate challenge. Collider experiments probe processes lasting around 10^-23 seconds, while dark matter has shaped the universe over billions of years. A lab discovery would need to be shown to behave correctly over cosmological timescales.
