Quantum Nondemolition Measurements of Macroscopic Objects
A "quantum nondemolition" (QND) measurement is a measurement that can be applied many times without perturbing the measured object. For example, measuring the distance to a mirror by reflecting light off it is not a QND measurement, because each reflected photon will 'push' slightly against the mirror and change its position (called "measurement backaction"). This is not a problem in classical measurements, but if we want to measure a quantum state, it turns out that we must be more careful! This backaction will blur all the quantum details.
We work on designing types of QND measurement that can be applied to engineered objects in the picogram to nanogram scale, such as mirrors, dielectric membranes, and nanophotonic structures. This will allow resolving quantum features of the wavefunction. More specifically, our resolution must be finer than the quantum vacuum fluctuations of the motion.
These measurements form only a part of a complete set of tools for manipulating macroscopic quantum systems by applying pulses of light—for example cooling by converiting motional quanta to photons.
Engineering Macroscopic Quantum States
In addition to measurement, we seek to create non-classical states of macroscopic motion. This can be done in various ways, for example by transferring a quantum state of light, or by entangling the object with the light and collapsing both systems onto a quantum state via photon detection.
More coming soon!