The observable universe is overwhelmingly dominated by matter, rather than consisting of equal parts matter and antimatter. To explain this cosmological imbalance, the Sakharov conditions dictate that there must be a violation of Charge-Parity (CP) symmetry. CP symmetry assumes that physical laws remain identical if a particle is swapped with its antimatter counterpart (Charge conjugation) and its spatial coordinates are inverted (Parity).

In the Standard Model (SM) of particle physics, CP violation occurs naturally during weak interactions. It is mathematically encoded by a complex phase within the Cabibbo–Kobayashi–Maskawa (CKM) matrix, which describes how quarks mix and transition between different flavours. This phenomenon was first observed in the decay of neutral kaons in 1964 and later definitively confirmed in B-meson decays by the BaBar and Belle experiments. Furthermore, due to the foundational CPT theorem, a violation of CP symmetry inherently demands a corresponding violation of Time-reversal (T) symmetry. The BaBar collaboration provided the first direct, unambiguous observation of this T-violation in 2012 by analysing the decay rates of entangled B-mesons.

However, the amount of CP violation generated by the CKM matrix is billions of times too minuscule to account for the universe's vast matter-antimatter asymmetry. This discrepancy strongly implies the existence of undiscovered physics beyond the Standard Model (BSM).

To discover these new sources of CP violation, physicists conduct high-precision searches for permanent Electric Dipole Moments (EDMs) in fundamental particles like neutrons and electrons. A non-zero EDM implies a separation of positive and negative charge centres within a particle, which directly violates both Parity (P) and Time-reversal (T) symmetries.

Because the SM predicts exceptionally tiny EDMs (for example, approximately $10^{-31}$ e·cm for the neutron), detecting any measurable EDM with modern technology would be an undeniable signature of new BSM physics, such as Supersymmetry. To achieve this, ambitious projects like the n2EDM experiment at the Paul Scherrer Institute utilise ultracold neutrons stored in highly controlled magnetic environments to probe the neutron EDM. Concurrently, experiments like ACME use heavy polar molecules, which have massive internal electric fields, to set incredibly stringent limits on the electron EDM.