Report
Teaser, summary, work performed and final results
Periodic Reporting for period 1 - SUPEREOM (Microwave-to-Optical Quantum Link: Quantum Teleportation and Quantum Illumination with cavity Optomechanics)
Teaser
Qubits, or quantum bits, are the key building blocks at the heart of every quantum computer. In order to perform a computation, signals are directed to and from qubits. However, qubits are extremely sensitive to interference from their environment, and need to be shielded from...
Summary
Qubits, or quantum bits, are the key building blocks at the heart of every quantum computer. In order to perform a computation, signals are directed to and from qubits. However, qubits are extremely sensitive to interference from their environment, and need to be shielded from outside signals, in particular from magnetic fields. It is a serious problem that the devices built to shield qubits from unwanted signals, known as nonreciprocal devices, produce magnetic fields themselves. Moreover, they are several centimeters in size, which is problematic, given that a large number of such elements is required in each quantum processor. We have decreased the size of nonreciprocal devices by two orders of magnitude. Their device, which they compare to a traffic roundabout for photons, is only about a tenth of a millimeter in size, and—more importantly—it is not magnetic.
We have implemented the first nonreciprocal mechanical on-chip microwave circulator. Directional circulation is achieved with controlled phase-sensitive interference of six distinct electro-mechanical signal conversion paths. The presented circulator is compact, its silicon-on-insulator platform is compatible with both superconducting qubits and silicon photonics, and its noise performance is close to the quantum limit. This frequency tunable and in situ reconfigurable signal processing device can be used as a filter, wavelength converter, beam splitter, isolator or circulator for microwave photons and it paves the way to implement the on-chip microwave to optical converter.
Beside that we have developed the theory of and discuss a potential realization for the controllable flow of thermal noise in quantum systems. We have demonstrated theoretically that the unidirectional flow of thermal noise is possible within quantum cascaded systems.
Work performed
1) Set up the lab:
We have built a fiber coupling based room temperature test setup including two optical tables for characterizing photonic crystal cavities.
We also have managed to set up 2 dilution refrigerators and equipped them for sensitive microwave and optical measurements respectively. We have developed a comprehensive Python based measurement software package to characterize superconducting resonators, photonic crystals and electro- and optomechanical samples.
2) Simulation, design, and fabrication of EOM:
We extensively have simulated several geometry for the optical to microwave conversion based on the photonic crystal beam coupled to LC circuits. Using electron beam lithography and ICP RIE etching we have already fabricated photonic crystal cavities (see Fig. 3b) and characterized them at room temperature (on SOI).
3)Microwave photon conversion: We intensively worked on simulation, designing, and modelling the microwave resonators, on-chip electromechanical microwave to microwave converter, and superconducting transom qubits. We tested and characterized the sample in our dilution fridges and have achieved sideband cooling with mechanical occupations of ~ 0.6 phonons as well as wavelength conversion between GHz frequency microwave modes with ~ 70% total bidirectional conversion efficiency.
4)Nonreciprocal photon conversion: We have implemented the first mechanical on-chip and magnetic-free nonreciprocal photon based on the mechanical resonator coupled to microwave resonators.
Final results
With proper fabrication and optimization we expect to have first version of the optical to microwave converter within next 3 months. The results of the project will have important impacts on my future career. Build the optical-to-microwave converter will pave the way to implement the so-called quantum internet, where local quantum processors are connected to a long-distance network. These converters allow us to bridge the superconducting nodes (qubits) to optical fields. Fabricating and experimentally implementing these converters will be very an important step toward building quantum network and will lead to a large impact and visibility of my work.