US-12627379-B2 - Methods and systems for quantum transducers

Abstract

Systems and methods for transducing and storing qubit signals are provided. The system includes a voltage source, a substrate, and a membrane suspended over the substrate. A phononic crystal oscillator is disposed in a first region of the membrane. The phononic crystal oscillator includes a capacitor having a moving electrode including an array of multiple phononic crystal unit cells. The moving electrode is connected to the voltage source. A superconducting circuit disposed in a second region of the membrane. A plurality of phonon shields and an optical resonator may also be disposed on the membrane.

Inventors

• Mohammad Mirhosseini
• Alkim Bozkurt
• Han Zhao
• Chaitali Joshi

Assignees

• CALIFORNIA INSTITUTE OF TECHNOLOGY

Dates

Publication Date

20260512

Application Date

20230616

Claims (17)

1. 1 . A system for transducing and storing a qubit signal, the system comprising: a voltage source; a substrate; a membrane suspended over the substrate; a phononic crystal oscillator disposed in a first region of the membrane, wherein the phononic crystal oscillator comprises a capacitor having a moving electrode including an array of multiple phononic crystal unit cells, wherein the moving electrode is connected to the voltage source; and a superconducting circuit disposed in a second region of the membrane.
2. 2 . The system of claim 1 , wherein the phononic crystal oscillator has a mechanical resonance frequency in a range from about 5 GHz to about 8 GHz.
3. 3 . The system of claim 1 , wherein the capacitor further comprises a set of outer electrodes located on either side of the moving electrode.
4. 4 . The system of claim 3 , wherein each of the set of outer electrodes and the moving electrode are separated by a vacuum gap of less than 100 nm.
5. 5 . The system of claim 1 , wherein the first region is mechanically coupled to the second region.
6. 6 . The system of claim 1 , wherein the membrane comprises crystalline silicon.
7. 7 . The system of claim 6 , wherein the membrane has a thickness of about 220 nm.
8. 8 . The system of claim 1 , wherein the voltage source comprises a Direct Current (DC) voltage source.
9. 9 . The system of claim 8 , wherein the DC voltage is in a range from about 1 V to about 25 V.
10. 10 . The system of claim 1 , wherein the superconducting circuit comprises a ladder-shape topology.
11. 11 . The system of claim 10 , wherein the superconducting circuit comprises Titanium Nitride (TiN) nanowires.
12. 12 . The system of claim 11 , wherein the TiN nanowires have a thickness of about 15 nm.
13. 13 . The system of claim 1 , wherein the superconducting circuit is characterized by an impedance of about 2.5 kΩ.
14. 14 . The system of claim 1 , further comprising: a first plurality of phonon shields disposed in a third region of the membrane; and a second plurality of phonon shields disposed in a fourth region of the membrane.
15. 15 . The system of claim 14 , wherein: the third region is disposed on a first side of the first region; and the fourth region is disposed on a second side of the first region opposing the third region.
16. 16 . The system of claim 14 , wherein the first plurality of phonon shields and the second plurality of phonon shields are characterized by a mechanical bandgap between 4.3 GHz and 6 GHz.
17. 17 . The system of claim 1 , further comprising an optical resonator connected to the phononic crystal oscillator via a phonon waveguide.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS This application claims benefit under 35 USC § 119(e) to U.S. Provisional Patent Application No. 63/353,475 filed Jun. 17, 2022, entitled “Phononic Crystal Electrostatic Transducers for Quantum Memories,” and to U.S. Provisional Patent Application No. 63/394,238 filed Aug. 1, 2022, entitled “Electrostatic Electro-Optomechanical Crystal Transducer,” the disclosures of which are hereby incorporated by reference in their entirety for all purposes. STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT This invention was made with government support under Grant No(s). PHY1733907 & OMA2137776 & OMA2137645 awarded by the National Science Foundation. The government has certain rights in the invention. BACKGROUND OF THE INVENTION Phonons, the quanta of energy stored in vibrations in solids, promise unique opportunities for storing and communicating quantum information. The intrinsic mechanisms for phonon dissipation get suppressed at low temperatures, leading to extremely low acoustic loss in single crystalline materials. Additionally, the inability of sound waves to propagate in a vacuum makes it possible to trap phonons in wavelength-scale dimensions via geometric structuring, leading to near-complete suppression of environment-induced decay. Finally, phonons interact with solid-state qubits and the electromagnetic waves across a broad spectrum, making them near-universal intermediaries for cross-platform information transfer. Motivated by these properties, pioneering work in the past two decades has enabled sensitive measurement and control of mechanical oscillators in the quantum regime via optical and electrical interfaces, making them viable candidates for quantum sensors, memories, and transducers. While optomechanical experiments have been successful in measuring phonons with millisecond-to-second lifetimes, accessing long-lived mechanical resonances with electrical circuits has been more challenging. In the gigahertz frequency range, where the spectral proximity to superconducting qubits holds the most promise for quantum technologies, piezoelectricity is the predominant mechanism for converting microwave photons to phonons. Piezoelectric devices have been used with remarkable success in coupling mechanical modes to superconducting qubits. However, their need for hybrid material integration, sophisticated fabrication process, and reliance on lossy poly-crystalline materials has limited the state-of-the-art experiments to sub-microseconds mechanical lifetimes in devices with compact geometries. This evidently large gap between the mechanical lifetimes accessible to optical and electrical interfaces motivates pursuing less invasive forms of electromechanical interaction. Creating better electrical interfaces for long-lived phonons holds the potential for revolutionizing the current quantum toolbox by pairing the superior coherence of acoustics with the massive nonlinearity of Josephson junction circuits. Bi-directional conversion of electrical and optical signals is an integral part of telecommunications and is anticipated to play a crucial role in long-distance quantum information transfer. Direct electro-optic frequency conversion can be realized via the Pockels effect in nonlinear crystals. More recently, progress in controlling mechanical waves in nanostructures has led to a new form of effective electro-optic interaction, which is mediated via resonant mechanical vibrations. In this approach, the electrical actuation of mechanical waves in piezoelectric materials is combined with the acousto-optic effect in cavity optomechanical systems to modulate the phase of an optical field. Piezo-optomechanical systems based on this concept have been used for microwave-optics frequency conversion as well as optical modulation, gating, and non-reciprocal routing. A variety of materials such as lithium niobate, gallium arsenide, gallium phosphide, and aluminum nitride have been previously used in piezo-optomechanical devices. However, relying on a single material platform for simultaneously achieving strong piezoelectric and acousto-optic responses is challenging. Alternatively, heterogeneous integration has been used to combine piezoelectric materials with silicon optomechanical crystals. These devices benefit from the large optomechanical coupling rates facilitated by the large refractive index and photoelastic coefficient of silicon. However, they utilize sophisticated fabrication processes, which hinder mass integration with the existing technologies. Additionally, heterogeneous integration often results in poly-crystalline films and degraded surface properties, which lead to increased microwave, acoustic, and optical loss when operating in the quantum regime. In addition, connecting microwave electronics with optical fiber networks paves the foundation for high-speed communication infrastructures and future distributed quantum computat