Dephasing due to electromagnetic interactions in spatial qubits

Abstract

Matter-wave interferometers with microparticles will enable the next generation of quantum sensors to probe minute quantum phase information. Therefore, estimating the loss of coherence and the degree of entanglement degradation for such interferometers is essential. In this paper, we provide a noise analysis in frequency-space focusing on electromagnetic sources of dephasing. We assume that our matter-wave interferometer has a residual charge or dipole which can interact with a neighboring particle in the ambience. We investigate the dephasing due to the Coulomb, charge-induced dipole, charge-permanent dipole, and dipole-dipole interactions. All these interactions constitute electromagnetically driven dephasing channels that can affect single or multiple interferometers. As an example, we apply the obtained formulas to situations with two adjacent microparticles, which can provide insight for the noise analysis in the quantum gravity-induced entanglement of masses (QGEM) protocol and the c-not gate: we compute the dephasing due to a gas of environmental particles interacting via dipole-dipole and charge-charge couplings, respectively. To obtain simple analytical dephasing formulas, we employ uniform probability distributions for the impact parameter and for the angles characterizing the relative orientation with respect to the interferometer and a Gaussian distribution for the velocities of the environmental particles. In both cases, we show that the dephasing rate grows with the number density of particles present in the vacuum chamber, as expected.