High-rate entanglement between a semiconductor spin and indistinguishable photons

In this publication, we present cluster states of entangled photons represent the main building block for developing error corrected and large scale photonic quantum computers. We demonstrate the generation of three-photon cluster states using a single quantum dot based device, achieving two orders of magnitude with respect to previous state of the art among different quantum technology systems.

Photon-number entanglement generated by sequential excitation of a two-level atom 

Exploiting the atomic behaviour of a semiconductor quantum dot in a cavity, we develop a novel protocol for the generation of photon number entangled states in the time basis: from a photon number Bell state up to a series of multi-temporal mode entangled states. 

The results demonstrate the possibility of using single-photon sources to encode quantum information in new ways. 

Bright Polarized Single-Photon Source Based on a Linear Dipole 

Bright emission of polarized single-photons from quantum dots is demonstrated by taking advantage of phonon-assisted relaxation and the intrinsic linear dipole structure of exciton states. By optical pumping of the exciton state along one of its dipoles we achieve high emission efficiency of indistinguishable photons with linear polarization degree up to 99%, without the need of complex cavity engineering.

Reproducibility of high-performance quantum dot single-photon sources 

Solid-state quantum light emitters are ubiquitous quantum technology devices required for a large plethora of applications. Their integration in complex industrial systems is bounded by the improvement of their efficiency but also by reproducible and high-fidelity fabrication on a large scale. By leveraging the full potential of semiconductor processing and Quandela’s technology we demonstrate the scalable and reproducible fabrication of a large set of devices with top performances.

Generation of non-classical light in a photon-number superposition 

Quantum information can be encoded in several degrees of freedom of single photons; we demonstrate the possibility to generate pulses of light containing a superposition of Fock states of different photon number with high quantum purity. By varying the excitation regime we present the deterministic variation of the proportions in between Fock states |0>, |1> and |2>. 
The results show in this way a new degree of freedom for qubit encoding in quantum computing protocols.

Near-optimal single-photon sources in the solid state 

The first demonstration of bright solid-state quantum light emitter devices, engineered in a deterministic microcavity system, with record photon indistinguishability and single-photon purity. The first demonstration of a game changing technology.


Quantum Advantage in Information Retrieval

Random access codes have provided many examples of quantum advantage in communication, but concern only one kind of information retrieval task. We introduce a related task—the Torpedo Game—and show that it admits greater quantum advantage than the comparable random access code.

Perceval: A Software Platform for Discrete Variable Photonic Quantum Computing

We introduce Perceval, an evolutive open-source software platform for simulating and interfacing with discrete variable photonic quantum computers, and describe its main features and components. 

Quantifying n-photon indistinguishability with a cyclic integrated interferometer

Indistinguishable single photons are key resources in photonic implementations of quantum information algorithms. However fully general techniques to quantify indistinguishability are missing. Here we report such a technique, with new theoretical developments leading to an experimental demonstration.

Interfacing scalable photonic platforms: solid-state based multi-photon interference in a reconfigurable glass chip

An efficient realization of modular quantum photonic platform interconnecting quantum dot single-photon emitters, active demultiplexing and integrated waveguides on Silica. Due to high brightness and device efficiency we demonstrate a speed up, compared to similar experiments performed with probabilistic SPDC and four-wave mixing sources.


A Framework for Verifiable Blind Quantum Computation

While it is possible to benchmark devices or use certification techniques under various assumptions, the most stringent proof is given by verification protocols: they provide unconditional assurance that the client will either receive the correct outcome or abort the computation, even against a service provider which actively tries to corrupt the result. We provide the first framework for designing such protocols in a way that both encompasses most known protocols and allows to create new ones in a much simpler way. This streamlines the creation process and allows us to already improve on our previous state-of-the-art protocols for the verification of delegated quantum computation by introducing two new constructions.

Strong Simulation of Linear Optical Processes

In this paper, is provided an algorithm and general framework for the simulation of photons passing through linear optical interferometers. 

A Complete Equational Theory for Quantum Circuits

In this note, is introduced the first complete equational theory for quantum circuits. More precisely, a set of circuit equations that are proved to be sound and complete: two circuits represent the same quantum evolution if and only if they can be transformed one into the other using the equations.

A Graphical Language for Linear Optical Quantum Circuits

The LOv-calculus, a graphical language for reasoning about linear optical quantum circuits with so-called vacuum state auxiliary inputs.

Mitigating errors by quantum verification and post-selection

This paper proposes a technique for mitigating time dependent errors in quantum circuits, and tests this technique on currently available quantum hardware. 

Sequential generation of linear cluster states from a single photon emitter

Assessing the quality of near-term photonic quantum devices

The Photonic Quality Factor is a scalable single-number metric for assessing the performance of current and near-term photonic quantum computing devices. We propose a series of benchmark tests targetting two main sources of noise, namely photon loss and distinguishability. The PQF is the largest number of input photons for which the output statistics pass all tests. We provide strong guarantees that passing the tests precludes efficient classical simulability.

Who are we

Quandela brings state-of-the-art technology and combines it with the strong dedication of its teams. We build unique solid-state sources of quantum light and create quantum algorithms to power a new generation of quantum computers, available on the cloud.

Join our team

Be part of an experience: Quandela is a growing company with large ambitions and a limitless potential. If like us you’re a passionate scientist or technologist, hungry for a challenge and with long term vision, come work with us and together, we’ll tackle on the quantum revolution!

Who trusts us

From industries and commercial partners working with us to develop new quantum computing use-cases, to funding agencies and investors supporting the scale-up of our technology; to the scientific community integrating Quandela’s components and adopting our cloud solutions to tackle multiple quantum applications.

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Request access to our quantum computing platform and solutions by contacting our teams.