SP1: Quantum Metrology and Sensing

WP1.1: Quantum metrology in real-world environments

Quantum metrology was shown to enable unprecedented signal to noise ratio and resolution of measurements, at sensitivities unreachable with conventional measurement schemes. However, in real world applications, the quantum systems are exposed to various sources of noise and decoherence which threaten to erase the gain of the ideal system. It is thus indispensable to redesign and optimize quantum metrology systems to make them the tool of choice for real world applications. It is thus the objectives of this work package to

  • develop entanglement enhanced metrology for real world environment causing decoherence and loss
  • optimize quantum sensing for limited resources
  • design setups for entanglement enhanced metrology

WP1.2: Quantum sensor applications

The achievements from other WPs will be adopted with the main goal to demonstrate the feasibility of entanglement enhanced sensors, using state-of-the art photonic and atomic technologies. These will serve as test beds for elementary parameter estimation protocols, and then for more advanced robust protocols developed in WP1.1 and 1.4, with a view to practical applications in temperature, motion, position and rotation sensing. Particular goals are:

  • To develop entanglement-enhanced quantum sensors (EEQS) for temperature, positioning, displacement and magnetic and gravitational fields
  • To demonstrate EEQS in applications such as illumination, range-finding and microscopy

WP1.3: Metrology at the quantum-quantum interfaces

We will extend the objective of entanglement enhanced metrology to the measurement of quantum properties read out with quantum systems. The realization of this quantum-quantum interface resembles the original concept of a measurement in quantum physics described in the seminal works by von Neumann and allows reaching ultimate measurement sensitivity. In detail the we aim to

  • identify and describe candidates for quantum-quantum interfaces
  • implement a quantum-quantum interface by coupling nonclassical states of light with the quantised motion of nanomechanical systems.

WP1.4: Multi-parameter estimation and non-linear metrology

The next generation quantum metrology systems will extend the concepts and thus also the performance of today's systems by generalizing the evolution determined by the measurement parameters. For the definition of future quantum metrology systems it is thus of utmost importance to:

  • develop multi-paramter estimation of quantum state evolution
  • develop nonlinear interferometry to break the Heisenberg limit

SP2: Enabling Technologies for Quantum Communication

WP2.1: Quantum optical detectors and random number generators

We will develop photon detectors and random number generators with functionality and performance far beyond the current state of the art. We  focus effort on the two most promising technologies: superconducting nanowires and semiconductor avalanche photodiodes, for quantum memories and free space (500-1000nm) and fibre (approx. 1550nm) applications, i.e. with specific target applications in WP2.3, 2.5, 1.3 and 3.4. [D21.2] will provide a mid-project comparison and review of the state of the art for the detector development within the project and in the context of their target applications.

Photon number resolution (PNR) capability at 1550 nm has recently been demonstrated (by Q-ESSENCE partners) using parallel superconducting nanowire detectors (PND) and self-differencing APD (avalanch photo-diodes) detectors (SD-APD), but with limited detection efficiency (2-10%). In this project we will enhance the efficiencies (70-90%) to allow single-shot number detection and extend to shorter wavelengths. In addition we will increase the maximum count rate to Gcount/s. We will also build compact, robust single photon detection modules incorporating fast bias and detection electronics.

State-of-the-art Quantum Random Number Generators (QRNG) are currently limited to a few MHz. Quantis has been commercially available for a few years by Q-ESSENCE industrial partner (idQ). Though highly miniaturised and relatively cheap, its bit rate is limited to 4Mbps thus preventing integration in third generation QKD systems and other demanding cryptography applications. In this project we will explore new approaches and utilise new high count rate detectors to drastically increase the bit rate to >250Mbps and eliminate the need for post processing of the bits.

WP2.2: Quantum light sources

In this workpackage the key objective will be to develop sources suitable for long-range high-speed quantum communications. In general this will involve developing high efficiency, narrowband, integrated sources. However each end-application will have a specific set of requirements. Within this sub-project we identify long distance communication (free space and fibre), quantum interfaces and memory as well as repeaters as our target  application areas. Further applications in quantum metrology (WP1.2) and quantum information processing (WP3.4-5) will also be able to take advantage of these efforts.

The sources to be developed include those based on pair generation by spontaneous parametric processes in various non-linear materials, as well as those based on the emission of a single semiconductor quantum dot. The former have the attraction of producing high entanglement fidelity and pure states, while the latter can be used as an 'on-demand' source with high repetition frequencies. These will be generally in waveguide or compact form and could include associated circuits on the same 'chip'.

WP2.3: Quantum memories and interfaces

The maximal distance of point-to-point quantum communication is limited by unavoidable loss of information in the quantum channel due to attenuation. A potential solution to overcome this limitation is the use of quantum repeaters. This WP will develop quantum memories (QMs) and light-matter interfaces suitable for integration in quantum repeater architectures developed in WP2.4 and with a view of laboratory and field trials of quantum communication protocols in WP2.5 [D23.2]. Particular goals of this WP are:

  • To develop new QMs, which allow long-time storage of photonic quantum information
  • To develop new techniques for fast and efficient (deterministic) read-out of stored states
  • To develop efficient inter-conversion of qubit species via quantum light-matter and light-light interfaces capable of interfacing diverse systems such as QM and telecom systems.

These devices will be realised in different systems with an emphasis on high-fidelity operation (>90%), and scalability.

WP2.4: Design and comparison of quantum communication technologies

The objectives of WP2.4 are to theoretically study, design, develop and verify quantum communication technologies with particular emphasis on optimising architectures for the long distance distribution of entanglement. The two keys objectives are to develop:

  1. Designs for entanglement distribution architectures (both fibre and free-space), determine their limitations and provide techniques for their optimisation
  2. Methods for the quantitative verification of distributed entanglement

A close involvement with all experimental aspects of the project is  envisaged, thus providing a reference point for comparing enabling technologies and setting the device benchmarks necessary for successful demonstrations of key quantum communication primitives in WP2.5.

WP2.5: Quantum communication test beds

The objective of this WP is to demonstrate the advances towards enabling technologies for quantum communication that out perform current distance limitations [D25.3]. We will showcase the enabling technologies developed in WP2.1-3. This will be achieved by performing laboratory and field trials of fundamental quantum communication primitives determined in WP2.4
that surpass the associated benchmarks.

We are focusing on two solutions that take advantage of the existing global communication infrastructure: satellite-based free space systems and fibre optic telecommunication networks. We will also study and demonstrate techniques to deal with the constraints of real world operation: loss; stability; synchronisation, and decoherence on these channels.

Our objectives are:

  • High-Fidelity interconnectivity of multiple technologies: sources, QMs, interfaces and detectors
  • Management of quantum channels
  • Demonstrations of fundamental quantum communication primitives developed in WP2.4

SP3: Distributed Quantum Information Processing

WP3.1: Distribution of continuous-variable entanglement

This work package will explore the potential of continuous-variable  entanglement distribution, focussing on network compatibility and the ability of distillation, including approaches combined with photon counting,  multipartite and bipartite settings, in theory and experiment.

WP3.2: New protocols

In this work package, the full potential of distributed quantum protocols and their resource scaling requirements will be theoretically explored, beyond standard settings of communication and quantum cryptography.

WP3.3: Verification and identification methods

This work package will identify and develop a toolbox of verification methods that certify quantitatively that the experimental implementation of a protocol or physical procedure was successful. The emphasis will be on methods that are efficient in terms of experimental resources and, in particular, do not require full quantum tomography.

WP3.4: Implementations of distributed protocols

It is the objective of this work package to experimentally implement novel distributed protocols and to provide theoretical ideas leading to such an implementation. Ideas of optimal control will also contribute to a toolbox for such settings.

WP3.5: Entanglement-based quantum information processing

In this workpackage, basic entanglement primitives, the foundations of entanglement-based quantum information processing, and new quantum computational models will be explored.

SP4: Strategic Operations and Management

WP4.1: Coordination of project RTD activities

This workpackage is to provide RTD coordination for the project on central level and for the three scientific Sub-Projects SP1, SP2 and SP3.

WP4.2: Project management

The objective of this workpackage is to provide management for the entire project.

WP4.3: Dissemination activities

Dissemination activities of Q-ESSENCE at the top project level.

WP4.4: Meetings and training

Organization of project meetings and workshops, training schools, young researchers’ meetings and general mobilities. These activities will be overseen by the Meetings and Training Committee.

Project & realization: Pixels United.
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