A quantum system involving molecules, used for sensing dark matter or interfacing with photons.A molecular quantum system is a collection of molecules whose quantum properties — such as energy levels, spins, or vibrational states — are harnessed for a specific purpose, often in sensing or quantum information processing. In the context of dark matter detection, certain molecules can act as sensitive probes: their rotational or spin states can be perturbed by passing dark matter particles, and this perturbation can be read out as a signal. More broadly, molecular quantum systems are being explored for quantum computing, precision measurements, and simulating complex quantum phenomena.
The use of molecules as quantum sensors emerged in the 2000s, building on decades of work in molecular spectroscopy and laser cooling. The specific proposal to use molecular quantum systems for dark matter detection was advanced in the 2010s, as part of a broader effort to find new ways to probe the elusive particle.
Molecules offer a rich set of internal degrees of freedom — electronic, vibrational, and rotational — that can be controlled with lasers and electromagnetic fields. For dark matter detection, the idea is to use molecules with a permanent electric or magnetic dipole moment, which couples to the weak interactions of dark matter particles. When a dark matter particle scatters off a molecule, it can change the molecule's rotational state or spin orientation, and this change can be detected via spectroscopy. In quantum sensing, molecules can be prepared in superposition states that are exquisitely sensitive to external fields, allowing measurements of magnetic fields, electric fields, or even forces at the quantum limit.
Molecular quantum systems are used in atomic clocks, magnetometers for medical imaging (like magnetoencephalography), and in the search for dark matter, where they offer a complementary approach to traditional detectors.
Some molecular quantum systems can be used to create 'quantum batteries' — devices that store energy in the quantum states of molecules, potentially charging faster than classical batteries.
