SCALABLE MULTI-CHIP QUANTUM ARCHITECTURES ENABLED BY CRYOGENIC WIRELESS / QUANTUM -COHERENT NETWORK-IN PACKAGE

Project Information

QUADRATURE

Grant agreement ID: 101099697

DOI

10.3030/101099697

EC signature date 9 December 2022

Start date 1 June 2023

End date 31 May 2027

Funded under

• The European Innovation Council (EIC)

Total cost

€ 3 420 513,75

EU contribution

€ 3 420 513,75

Coordinated by

UNIVERSITAT POLITECNICA DE VALENCIA
Spain

Periodic Reporting for period 2 - QUADRATURE (SCALABLE MULTI-CHIP QUANTUM ARCHITECTURES ENABLED BY CRYOGENIC WIRELESS / QUANTUM -COHERENT NETWORK-IN PACKAGE)

Reporting period: 2024-06-01 to 2025-11-30

Summary of the context and overall objectives of the project

Today’s tremendous interdisciplinary effort towards building a quantum computer promises to tackle problems beyond reach of any classical computer. Although intermediate-scale quantum computers have been demonstrated to exceed the capability of the most powerful supercomputers (quantum advantage), it is widely recognized that addressing any real-world problem will require upscaling quantum computers to thousands or even millions of qubits. QUADRATURE focuses on the grand challenge of scalability in quantum computers, from a full- stack architectural standpoint, and enabled by communication networks operating within the quantum computing package at cryogenic temperatures. This project hence aims to pioneer a new generation of scalable quantum computing architectures featuring distributed quantum cores (Qcores) interconnected via quantum-coherent qubit state transfer links and orchestrated via an integrated wireless interconnect. This novel architecture supports reconfigurability to serve massive flows of heterogeneous quantum algorithmic demands.

The main objectives are:
1. To experimentally prove the first micro-integrated all-RF qubit-state transfer link within a cryogenic tunable superconducting cavity waveguide in the microwave and THz frequency region for quantum-coherent frequency-multiplex and routing.
2. To achieve experimentally the transfer of classical data through wireless in-package links by integrated cryo-antennas and tranceivers;
3. To build protocols for a quantum-coherent integrated network enabling the exchange of qubits through the coordination of the quantum-coherent data plane and the wireless control plane;
4. To develop appropriate scalable architectural methods such as mapping, scheduling, and coordination approaches across multiple Qcores;
5. To demonstrate the scalability of the approach via multi-scale design space optimization and for a set of quantum algorithm benchmarks, with at least 10x improvement in overall performance.

QUADRATURE will pave the way to scalable quantum computing systems needed for unleashing the enormous potential of quantum computing in scientific and technological fields such as chemistry, material science, and artificial intelligence (AI).

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Developing a multi-core scalable quantum computer requires the collaboration of several groups with complementary expertise that include quantum hardware, cryo-CMOS, quantum computer architecture, wireless network-on-chip, integrated antennas, RF trancesiver SOCs and quantum algorithms/applications. This first period of the project has been mostly devoted to the definition of specifications and modelling several parts of the quantum computing system and the development of related simulation methods and tools.

The main achievements of the project in this second reporting period months can be summarised as follows:

- Demonstrating qubit-state transfer between different cores:
o The first test devices for flopping mode spin qubit transfer in SiGe have been designed, including circuit quantum electrodynamic modeling.
o An analytic model for the quantum transfer process for the swap of spin states has been derived.
o A stable and robust deposition technology for superconducting material has been stablished and optimised.
o Two integration approaches for a high-Q quantum cavity and coherent communication channel have been explored.

-Transfer of classical data hrough wireless in-package links:
o The RF duplexer has been designed, fabricated, and experimentally verified at room temperature, demonstrating how the antenna and the wireless channel can be used simultaneously for reception and transmission.
o The Low-Noise Amplifier (LNA) in the RF receiver has been optimized by introducing a novel current-reuse noise-cancelling architecture.
o The Analog-to-Digital Converter (ADC) in the RF receiver has been designed and taped out.
o The digital backend implementing the modulation and demodulation has been designed and fabricated.
o The RF transmitter (Tx) has been designed and taped out.
o The architecture for power delivery to the cryo-CMOS transceiver has been analyzed as a crucial step of the system integration.

- Protocols for a quantum-coherent integrated network:
o An EM field-solver numerical model and characterization of wireless propagation within a realistic cryostat at cryogenic temperatures has been proposed.
o A QED-based behavioral model of the cavity-mediated quantum state transfer physical link has been derived and fully characterized with QuTIP numerical simulations.
o A framework has been proposed and developed for a comprehensive characterization and optimization of the impact of classical and quantum communication networks upon modular quantum computing architectures.
o Additional incursions into thermal modelling and crosstalk modelling affecting the physical layers of both the classical wireless and the quantum link have been proposed.

- Innovative scalable architectural methods such as mapping and scheduling:
o A quantum benchmark suite has been created to guide the design and optimization of the multi-Qcore architecture.
o A scalable simulation framework of network design for modular quantum computing architectures integrating cavity-mediated interconnects has been conceived and developed.
o An accurate and scalable quantum circuit fidelity model has been developed to assess the performance of large-scale quantum computing systems.
o Two new quantum circuit mapping techniques have been proposed for performing distributed quantum computing targeting the QUADRATURE multi-Qcore architecture.

- Demonstrate the scalability of the QUADRATURE approach:
o Initial study of design parameters and metric ranges optimal for the operation of multi-Qcore architectures under the framework of Design Space Exploration.
o Study of tensor network architectures optimal for representing faithfully complex quantum states such as the ones appearing along a computation.
o Development of a numerical library for automatic differentiation of Tensor Networks (TN), enabling the training and optimization of complex tensor-network structures.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

During the period M13-M30, the consortium members contributed to a total of 26 publications of which 7 are journal articles, 14 conference publications and 5 pre-pints.

In addition, the consortium members took part in 21 scientific events (debate panel, invited talks/lectures, workshops, seminars).

The innovations arising from the projects are divided into three streams: quantum technology, systems and electronics and benchmarking and standards. The category on quantum technology includes the innovations on the technology, fabrication process and design of qubit and coupler structures. The IP types will include know-how and patents. The category on systems and electronics includes innovations on IC and circuits design for the full system. Finally, the category on benchmarking and standards will predominately include open source products.

Since the beginning of the project, thirteen potential innovation pathways have been identified. These have now been consolidated into a core group of contributions demonstrating high technical maturity, clear IP potential, or strong commercial relevance. The current pipeline of innovations include seven items split approximately equally across the three categories.

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