Transverse Magnetic Susceptibility in an Ising Spin Liquid

We study the AC vector magnetic susceptibility of the dilute Ising magnet $\mathrm{LiHo_{0.045}Y_{0.955}F_4}$. Driving the system into the nonlinear regime excites coherent oscillations of hundreds of spins. We find that these clusters can be projected from the Ising axis into the transverse plane by applying a DC transverse field. The lineshape of the oscillations changes as a function of this transverse field, indicating the presence of additional excitation modes. We study as well the time dependence of the excitation spectra and find a pronounced asymmetry along and transverse to the Ising axis. The spin liquid not only permits the encoding of information labeled by frequency, but is amenable to manipulation of quantum superposed states.