Periodic Reporting for period 1 - HyQuArch (Spin-based quantum memory coupled to superconducting qubits in a Hybrid Quantum Architecture)
Reporting period: 2022-11-01 to 2024-10-31
This project focuses on the development of a hybrid platform comprising various superconducting devices fabricated on diamond, intended for use as a quantum random access memory unit in quantum computing. The superconducting devices are of two primary types. First, superconducting resonators, which are crucial for operational and read-out tasks, enabling the manipulation and subsequent retrieval of quantum information. Second, superconducting qubits, including flux qubits and transmons, which form the foundational elements of solid-state quantum computers.
On the other hand, the diamond substrate has pre-implanted Nitrogen-Vacancy (NV) centers that can store quantum information originating from the superconducting qubits for later access. Typically, superconducting qubits do not offer long coherence times, meaning that quantum information has a short life span within these devices. NV centers, however, exhibit significantly longer coherence times, thus providing a memory bank where quantum information can be stored for extended periods. This capability allows NV centers in the diamond to function as a quantum memory, enabling the storage of quantum information while other calculations are conducted using the superconducting qubits.
In essence, the integration of superconducting devices with diamond NV centers leverages the strength of both components, facilitating the development of an efficient quantum random access memory system. This hybrid approach addresses the coherence limitation of superconducting qubits by utilizing the long coherence time of NV centers, thereby enhancing the overall performance and scalability of quantum computing applications.
On the other hand, the diamond substrate has pre-implanted Nitrogen-Vacancy (NV) centers that can store quantum information originating from the superconducting qubits for later access. Typically, superconducting qubits do not offer long coherence times, meaning that quantum information has a short life span within these devices. NV centers, however, exhibit significantly longer coherence times, thus providing a memory bank where quantum information can be stored for extended periods. This capability allows NV centers in the diamond to function as a quantum memory, enabling the storage of quantum information while other calculations are conducted using the superconducting qubits.
In essence, the integration of superconducting devices with diamond NV centers leverages the strength of both components, facilitating the development of an efficient quantum random access memory system. This hybrid approach addresses the coherence limitation of superconducting qubits by utilizing the long coherence time of NV centers, thereby enhancing the overall performance and scalability of quantum computing applications.
The project significantly advanced the development of the basic ingredients of a hybrid quantum platform able to process quantum information with superconducting qubits and to store the states in spin-based quantum memories with long coherence times. On the one hand, trasmon qubits were fabricated and fully characterized. Their coherence times were also improved by two orders of magnitude via the optimization of the circuit and of the control and readout setup. On the other hand, superconducting resonators were successfully fabricated onto diamond substrates. These resonators can act as the interface to couple the states of the qubit with those of NV color centers in diamond, which are known as very promising quantum memories. In addition, a method to optimize the coupling between superconducting resonators and spins, by exploiting superposition spin states that arise near level anticrossings, was shown experimentally.
Development of high-quality superconducting lumped element resonators onto diamond susbtrates: besides their interest as an interface to mediate coherent communication between operational qubits and spins, this results offers the opportunity to use these hybrid devices as quantum memories or as highly sensitive magnetometers.
Method for optimizing the coupling of spin qubits to superconducting quantum circuits: this result shows that it is possible to optimize both the coupling to the circuit, which provides the ability to control and read out the spins, and the isolation from magnetic noise. This is a quite unique situation, as often the enhancement of the quantum operations speed comes at the cost of incrementing the coupling to decoherence sources. It might be of interest to any technology that is based on the detection of spins by quantum circuits, including quantum memories, quantum sensing, etc.
Method for optimizing the coupling of spin qubits to superconducting quantum circuits: this result shows that it is possible to optimize both the coupling to the circuit, which provides the ability to control and read out the spins, and the isolation from magnetic noise. This is a quite unique situation, as often the enhancement of the quantum operations speed comes at the cost of incrementing the coupling to decoherence sources. It might be of interest to any technology that is based on the detection of spins by quantum circuits, including quantum memories, quantum sensing, etc.