The motion of trapped ion crystals, when isolated from the environment, is governed by quantum mechanics. The vibration modes of the crystal can be viewed as quantum harmonic oscillator modes, with their bosonic excitations referred to as phonons. Traditionally, phonons are utilized as a quantum bus to facilitate interactions between cold trapped-ion spins. Instead, in our approach phonons serve as the primary resource, with their quantum state used as computational units, and their couplings mediated via the spins. As the number of phonons scale up with the size of the crystal, the combined spin and bosonic degrees of freedom in a trapped ion crystal represent an exceptionally large computational (Hilbert) space. We have recently developed efficient methods to program quadratic long-range couplings between long-lived collective phonon modes, enabling the realization of tasks such as boson sampling and various families of long-range bosonic Hamiltonians that are computationally hard.

Processing information with Phonons. Trapped ion crystals have collective modes of vibration, whose excitations are considered as phonons. Via controllable coupling to spins (right) different, non-local phonon modes can be coupled efficiently forming the basis to use phonon in quantum information science. See Phys. Rev. Lett. 131.033604 (2023) for more details.

Selected Publications

• “Programmable Quantum Simulations of Bosonic Systems with Trapped Ions“. Katz, Monroe. Phys. Rev. Lett. 131, 033604 (2023).