SQMS Center

Quantum sensing for fundamental physics

Quantum for fundamental scientific discovery

Quantum sensing of elusive particles is currently limited by the ability to store and detect single microwave photons and depends strongly on quantum devices’ coherence. Center scientists will make use of the SQMS quantum technologies advancements for physics applications. They will design and deploy sophisticated quantum devices and control techniques capable of improving current detection sensitivities up to orders of magnitude, with consequent increased discovery potentials.

Not only can research conducted by SQMS scientists be applied toward the construction of a state-of-the-art quantum computer, it can be applied to exploring our universe: looking for new particles, searching for dark matter, observing gravitational waves and more.

SQMS host institution Fermilab is a particle physics laboratory that has been at the center of particle physics pursuits and discoveries that advance—and hopefully go beyond—our understanding of the tried-and-tested Standard Model of particle physics.

As the scientific home for experts on superconducting cavities for accelerators and QIS, Fermilab brings researchers with expertise in particle physics, cosmology and SRF cavity technology together to broaden our understanding of the universe.

The particle accelerators at Fermilab use superconducting radio-frequency niobium cavities to push particles near the speed of light and smash them against different targets. Researchers then study their behavior.

These cavities are now being developed further by SQMS scientists to store information that is core to quantum computing. Combined with the best qubits made by SQMS collaboration experts, here are some ways SQMS researchers are using quantum technology to broaden our understanding of physics.

Searching for new particles

Over decades of experimentation and theory, physicists have developed the Standard Model of particle physics. The model consists of a specific list of particles and rigid rules by which they interact. SQMS scientists are addressing the naïve but important question: “Are there any more particles that we do not know of?” The Standard Model contains several copies of particles with similar properties but different masses, the electron and the muon, for example. Photons are particles of light, or electromagnetic energy, that might have mirrored copies called dark photons. Dark SRF is a ‘light-shining-through-wall’ experiment that’s searching for the existence of these dark photons. In this experiment, many photons are held inside one cavity, with a nearby identical cavity that is empty, in the quantum regime. If a dark photon exists, it will lead to a leakage of light from one cavity to the other. The very high cavity coherence or the single photon counting ability, or the two things combined, make this the most sensitive experiment of its kind.

Searching for dark matter

Dark matter is an invisible form of matter that is unidentified, yet comprises 85% of all matter in the universe. It is observed via its gravitational attraction through the rotation of stars in galaxies, when it bends light and the way it holds together the cosmic web of galaxies that make up the known universe. A theorized dark matter particle called the axion could be detected with cavities made of superconducting materials through searches developed by SQMS scientists. When axions travel through a strong magnetic field, there’s a chance they materialize as photons or particles of light. The frequency of these photons is related to the mass of the axion, which is unknown. If the frequency of the photons from the axion conversions match the resonance frequency of a cavity, the photons can collect within the cavity.

SQMS researchers are combining devices that have been developed for a quantum computer with ultra-high quality factor cavities—the quality factor being the ability to store electromagnetic energy within a cavity—with the objective of achieving the first detection of dark matter in a laboratory setting. By searching unexplored frequencies, using new materials and scanning different axion masses, researchers hope to uncover the properties of dark matter.

Detecting gravitational waves

Leveraging extremely sensitive SRF cavities in the quantum regime, SQMS researchers are also finding ways to observe gravitational waves, which are ripples in the fabric of spacetime predicted to exist in Einstein’s theory of general relativity.

The force of gravity arises when a massive object warps spacetime around it. The theory postulates that ripples in spacetime can form and travel great distances. One example is when two black holes collide. These ripples have been detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO), recognized with the Nobel Prize in Physics 2017.

Now, SQMS researchers are working to observe gravitational waves—in a much higher frequency than those seen by LIGO—by collecting photons, which are created when a strong magnetic field interacts with a gravitational wave, in a cavity. A similar setup to the axion searches described above will also be used to observe gravitational waves.

Single-particle and cavity systems for electron properties

The unique expertise brought together by SQMS will enable a new generation of experiments to probe fundamental properties of the Standard Model much more precisely. The Northwestern fundamental physics group has measured electron and positron magnetic moments, making the most precise determination of the properties of elementary particles. This allows researchers to test the most precise prediction of the Standard Model, to test the fundamental symmetry invariance of the Standard Model with leptons, and to constrain the presence of new interactions. SQMS collaborators at Northwestern and Fermilab are designing microwave cavities (traps) so that sections of the cavity walls can be biased to suspend a single elementary charge at the center of the cavity. The highest possible cavity quality factor will be sought with novel materials to maximize the suppression of spontaneous emission from an excited cyclotron state and hence to maximally reduce the line width of the measured electron resonances that determine the moment. Leveraging the SQMS technology thrust work, this will revolutionize fundamental low-energy particle physics measurements.