Microwave Quantum Photonics for Quantum Technology and Fundamental Physics

Projektinformationen

QPHOTON

ID Finanzhilfevereinbarung: 101087343

DOI

10.3030/101087343

EK-Unterschriftsdatum 25 Februar 2023

Startdatum 1 Juli 2023

Enddatum 30 Juni 2028

Finanziert unter

• European Research Council (ERC)

Gesamtkosten

€ 2 533 247,50

EU-Beitrag

€ 2 533 247,50

Koordiniert durch

LUNDS UNIVERSITET
Sweden

Periodic Reporting for period 1 - QPHOTON (Microwave Quantum Photonics for Quantum Technology and Fundamental Physics)

Berichtszeitraum: 2023-07-01 bis 2025-12-31

Zusammenfassung vom Kontext und den Gesamtzielen des Projekts

Microwave photons play a major role throughout all solid-state quantum technology architectures, including superconducting qubits as well as charge and spin qubits in semiconductors, where they are used for control, coupling and readout. This project aims to create sensors probing the timing between microwave photons thus building novel measurement tools applicable throughout the quantum technology field. In particular, continuous photon counting is developed. This could open up e.g. the avenue to implement quantum computing based on so-called boson sampling with superconducting circuits, combining two key requirements for practical quantum computing: the programmability of the superconducting circuits and the stronger quantum advantage of quantum processors based on boson sampling.

Beyond enabling the new measurement capabilities, on the fundamental side we explore fundamental physics questions. The interplay between correlated bosonic and fermionic states — e.g. on how the bosonic particle statistics of the photons map onto the fermionic ones of the electrons — is likely to spur new experimental activities around many-body physics. Furthermore, developing ultra-fast charge and photon detectors will also shed light on the still unknown physics question on how measurements really work and act in the quantum physics domain.

Arbeit, die ab Beginn des Projekts bis zum Ende des durch den Bericht erfassten Berichtszeitraums geleistet wurde, und die wichtigsten bis dahin erzielten Ergebnisse

So far, the project has achieved continuous counting of the microwave photons with low quantum efficiency. The continuous photocounting relates to seemingly different theories, the so-called P(E) theory that makes a probabilistic description of energy absorption and emission, and the input-output theory with Jaynes-Cummings Hamiltonian that is rather used for describing the coherent interaction of the photons in a resonator with an electric system. Our photoabsorber operates in a regime where these two theories coincide yielding a connection of the two descriptions.

In addition, we have developed a novel charge readout technique. This technique uses a non-linear resonator to obtain a near unity readout signal and ultra-fast speed in the nanosecond time domain. This technique allow to do the fast charge detection free of the usual limitations set by the requirement to match the sensor dissipation rate and the coupling rate of the readout port.

Fortschritte, die über den aktuellen Stand der Technik hinausgehen und voraussichtliche potenzielle Auswirkungen (einschließlich der bis dato erzielten sozioökonomischen Auswirkungen und weiter gefassten gesellschaftlichen Auswirkungen des Projekts)

The continuous and efficient microwave photocounters of this project may yield significant new tools to use for e.g. solid-state quantum device as well as to study other microwave signals that are found e.g. in the cosmic microwave background. The experiments of quantum measurements may also provide new fundamental physics insights to how the quantum measurements truly work. In particular, we can study the case where two continuous measurements are running either separately versus at the same time. These measurements are the position of the charge in the absorber and the energy that the absorber has.

More concretely, the project has already yielded a new way to perform ultra-fast charge readout, free of the usual design constraint forcing to match the sensor dissipation and the readout line coupling. Waiving this limitation opens up an avenue to design and construct the charge detection in a new way as the usual constraint can be now avoided.