Quantum Phononic Sciences
Abstract
The vibrations of man-made and macroscopic objects have recently come under quantum control. It is possible to measure, prepare, and manipulate the quantum state of individual phonons. But the performance of quantum acoustical systems lags far behind state-of-the-art quantum electrical circuits. The proposed work will advance this new science of quantum sound from rudimentary capabilities to a qualitatively new regime of high-fidelity quantum control of single phonons. The proposed work will yield a 10,000-fold increase in the coherent cooperation between superconducting qubit circuits and phononic cavities, while preserving the useful ways that acoustical phenomena differ from electronics and optics. Sound is different. The speed of sound is 100,000 times slower than light, thus phononic cavities are much smaller than electronic cavities of the same resonance frequency and therefore can be packed much more densely. Furthermore, information stored on a chip in phononic cavities is better isolated than in resonant electrical circuits. Chips host two-dimensional metallic structures but electromagnetic coupling occurs above and below the chip’s surface. In contrast, unwanted acoustical coupling can occur only through elastic waves inside the volume of the chip. Moreover, the chip itself can be patterned with micron-scale periodic structures that create a bandgap in the gigahertz frequency acoustical spectrum, providing superb isolation. Finally, the size of superconducting qubit circuits is larger than the acoustical wavelengths; thus, qubits do not couple to all parts of the acoustic spectrum through structureless dipole coupling, but only to specific wavevectors, chosen at the time of fabrication. This capability means, for example, that the spontaneous emission of phonons by qubits can be eliminated while the qubit retains strong dispersive coupling to phononic cavities. The proposed work advances quantum sound by: 1.) understanding and eliminating sources of decoherence in both phononic cavities and the qubits that couple to them 2.) validating the increased coherence by creating non-Gaussian states of motion and highly entangled states relevant to quantum error correction 3.) investigating unique qubit-phonon interactions enabled by quantum acoustics. In the regime of high-fidelity phonon control, quantum information can be encoded in logical qubits and preserved using error-correction algorithms or encoded in highly non-classical states with quantum enhanced strain sensitivity. In addition, the most promising way to transduce quantum information between the optical and electrical domains is through a quantum phononic intermediary systems. Successful outcome of this research would have a profound but hard to anticipate impact on information processing, information security, and sensing.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 11, 2020
- Source ID
- N000142012833
Entities
People
- Konrad W. Lehnert
Organizations
- Office of Naval Research
- Regents of the University of Colorado
- United States Navy