Chip-scale phonon-based quantum device
A quantum device includes a phononic crystal defined on a semiconductor substrate. Phononic cavities are defined in the phononic crystal, wherein each phononic cavity contains an implanted acceptor atom. Phononic waveguides are defined in the phononic crystal, wherein each waveguide is coupled to at least one phononic cavity. At least some phononic waveguides are arranged to provide coupling between phononic cavities and ultrasonic transducers. At least some phononic waveguides are arranged to provide coupling between different phononic cavities.
1. A quantum device, comprising:
a phononic crystal defined on a semiconductor substrate;
a plurality of phononic cavities defined in the phononic crystal, wherein each phononic cavity contains an implanted acceptor atom; and
a plurality of phononic waveguides defined in the phononic crystal, wherein each waveguide is coupled to at least one phononic cavity;
wherein at least some phononic waveguides are arranged to provide coupling between phononic cavities and ultrasonic transducers; and
wherein at least some phononic waveguides are arranged to provide coupling between different phononic cavities.
2. The quantum device of claim 1 , further comprising at least one ultrasonic transducer acoustically coupled to one or more of the phononic waveguides.
3. The quantum device of claim 2 , wherein at least one said ultrasonic transducer is an aluminum nitride interdigitated transducer.
4. The quantum device of claim 1 , further comprising a plurality of MEMS beams, each of which is configured to controllably and reversibly make mechanical contact with a respective one of the phononic waveguides.
5. The quantum device of claim 1 , wherein the semiconductor substrate is a suspended silicon membrane.
6. The quantum device of claim 5 , wherein the acceptor atoms are boron atoms.
7. The quantum device of claim 1 , wherein:
at least some of the phononic waveguides arranged to provide coupling between phononic cavities and ultrasonic transducers are tuned to a local initialization frequency; and
at least some of the phononic waveguides arranged to provide coupling between different phononic cavities are tuned to an entanglement frequency that is unequal to the local initialization frequency.
8. The quantum device of claim 7 , further comprising:
at least one ultrasonic transducer acoustically coupled to one or more phononic waveguides tuned to a local initialization frequency; and
at least one ultrasonic transducer acoustically coupled to the semiconductor substrate and tuned to a global initialization frequency that propagates in the phononic crystal without waveguide confinement.
9. The quantum device of claim 1 , wherein the phononic crystal is defined by a regular two-dimensional lattice of holes in the semiconductor substrate, the phononic cavities are defined by the absence of holes in cavity regions, and the phononic waveguides are defined by a change in hole dimensions in waveguide regions.
10. The quantum device of claim 1 , wherein:
the phononic cavities have a resonant frequency; and
the waveguides arranged to provide coupling between different phononic cavities are configured to have only one mode capable of oscillating at the cavity resonant frequency.