Hardware-Efficient Quantum Random Access Memory with Hybrid Quantum Acoustic Systems

Abstract

Hybrid quantum systems in which acoustic resonators couple to superconducting qubits are promising quantum information platforms. High quality factors and small mode volumes make acoustic modes ideal quantum memories, while the qubit-phonon coupling enables the initialization and manipulation of quantum states. We present a scheme for quantum computing with multimode quantum acoustic systems, and based on this scheme, propose a hardware-efficient implementation of a quantum random access memory (qRAM). Quantum information is stored in high-Q phonon modes, and couplings between modes are engineered by applying off-resonant drives to a transmon qubit. In comparison to existing proposals that involve directly exciting the qubit, this scheme can offer a substantial improvement in gate fidelity for long-lived acoustic modes. We show how these engineered phonon-phonon couplings can be used to access data in superposition according to the state of designated address modes-implementing a qRAM on a single chip.

Two-dimensional optomechanical crystal cavity with high quantum cooperativity

“…Optical-absorption-induced hot bath. While the acoustic mode Q-factor measured in ringdown measurements is promising for certain quantum memory applications 34,35 , it is measured with the laser pump off. The prospects for performing coherent quantum operations between photons and phonons depends critically on the ability to minimize unwanted heating and damping of the acoustic mode due to parasitic effects resulting from optical absorption in the presence of an applied laser field.…”

“…Owing to the large ratio (×10 5 ) of the speed of light to the speed of sound in most materials, OMCs operating at telecom-band optical frequency naturally couple strongly to similar wavelength microwave-frequency acoustic modes. Recent experimental demonstrations of microwave-frequency phononic crystal cavities with ultralow dissipation 32 and strong dispersive coupling to superconducting qubits 33 indicate that there are potentially significant technical advantages in forming an integrated quantum electrodynamic and acoustodynamic circuit architecture for quantum information processing 34,35 . In such an architecture, OMCs could provide a quantum interface between microwave-frequency logic circuits and optical quantum communication channels.…”

Hybrid integrated photonics using bulk acoustic resonators

“…The roll-off starting around 3.5 GHz is caused by reduced FSR due to coupling of the AlN cavity. This study of mechanical dispersion could benefit the growing field of mechanical dispersion engineering for future applications (e.g., mechanical dissipative solitons 40,41 , HBAR-based quantum random access memory 39,42 ) and future devices improvement by optimizing Si, SiO 2 , and AlN thicknesses or by choosing materials with different acoustic impedance. In this sense, further theoretical and numerical studies are necessary for a more complete understanding of the acoustic wave propagation and mechanical cavity coupling in such a platform.…”

Acoustic diamond resonators with ultrasmall mode volumes

“…Possible improvements could be achieved by embracing the recently developed concepts of soft-clamping [46] and strain engineering [47]. Furthermore, in materials for which fabrication techniques are more mature, such as silicon, much higher quality factors of PnC resonators up to 10 10 were reported recently [5], suggesting that GHz acoustic vibrations can be used as quantum memories [48] rather than transducers [2]. Finally, in a recent theoretical proposal, Neuman et al [49] proposed utilizing heterogeneous structures in which silicon phononic crystals would be interfaced with diamond patches hosting atomic defects.…”