摘要： The usually employed methods of using spin states of atomic-like systems for quantum information encoding suffer from scalability issues. For example, it becomes very challenging to control a large number of trapped atomic ions each representing a physical qubit. The alternative approach would be to exploit the large Hilbert space provided by a near-harmonic trapping potential and encode the information in the oscillator states. We use sideband-resolved addressing of motional states in a single trapped 171Yb ion to demonstrate a conditional beam splitter gate. The conditional beam splitter (CBS) Hamiltonian |e??e|(a?b + ab?) swaps the quantum states of two motional modes of a trapped ion, conditioned on the ion’s internal state. It thus can be viewed as a SWAP gate and we utilize it to demonstrate SWAP tests, implement single shot parity measurements, and generate maximally entangled NOON states of motion. We discuss the spurious phase shifts that prevent the gate to be dubbed as universal and show that with an addition of an ancilla vacuum mode, the conditional beam splitter gate in trapped ion system can be used to construct a universal exponential-SWAP gate that is required for practical algorithms such as matrix inversion and other interesting applications.