Showing 1–9 of 9 results for author: Stroj, S

Quantum teleportation with dissimilar quantum dots over a hybrid quantum network

Authors: Alessandro Laneve, Giuseppe Ronco, Mattia Beccaceci, Paolo Barigelli, Francesco Salusti, Nicolas Claro-Rodriguez, Giorgio De Pascalis, Alessia Suprano, Leone Chiaudano, Eva Schöll, Lukas Hanschke, Tobias M. Krieger, Quirin Buchinger, Saimon F. Covre da Silva, Julia Neuwirth, Sandra Stroj, Sven Höfling, Tobias Huber-Loyola, Mario A. Usuga Castaneda, Gonzalo Carvacho, Nicolò Spagnolo, Michele B. Rota, Francesco Basso Basset, Armando Rastelli, Fabio Sciarrino , et al. (2 additional authors not shown)

Abstract: Photonic quantum information processing in metropolitan quantum networks lays the foundation for cloud quantum computing [1, 2], secure communication [3, 4], and the realization of a global quantum internet [5, 6]. This paradigm shift requires on-demand and high-rate generation of flying qubits and their quantum state teleportation over long distances [7]. Despite the last decade has witnessed an… ▽ More Photonic quantum information processing in metropolitan quantum networks lays the foundation for cloud quantum computing [1, 2], secure communication [3, 4], and the realization of a global quantum internet [5, 6]. This paradigm shift requires on-demand and high-rate generation of flying qubits and their quantum state teleportation over long distances [7]. Despite the last decade has witnessed an impressive progress in the performances of deterministic photon sources [8-11], the exploitation of distinct quantum emitters to implement all-photonic quantum teleportation among distant parties has remained elusive. Here, we overcome this challenge by using dissimilar quantum dots whose electronic and optical properties are engineered by light-matter interaction [12], multi-axial strain [13] and magnetic fields [14] so as to make them suitable for the teleportation of polarization qubits. This is demonstrated in a hybrid quantum network harnessing both fiber connections and 270 m free-space optical link connecting two buildings of the University campus in the center of Rome. The protocol exploits GPS-assisted synchronization, ultra-fast single photon detectors as well as stabilization systems that compensate for atmospheric turbulence. The achieved teleportation state fidelity reaches up to 82+-1%, above the classical limit by more than 10 standard deviations. Our field demonstration of all-photonic quantum teleportation opens a new route to implement solid-state based quantum relays and builds the foundation for practical quantum networks. △ Less

Submitted 19 November, 2024; originally announced November 2024.

Wavevector-resolved polarization entanglement from radiative cascades

Authors: Alessandro Laneve, Michele B. Rota, Francesco Basso Basset, Mattia Beccaceci, Valerio Villari, Thomas Oberleitner, Yorick Reum, Tobias M. Krieger, Quirin Buchinger, Saimon F. Covre da Silva, Andreas Pfenning, Sandra Stroj, Sven Höfling, Armando Rastelli, Tobias Huber-Loyola, Rinaldo Trotta

Abstract: The generation of entangled photons from radiative cascades has enabled milestone experiments in quantum information science with several applications in photonic quantum technologies. Significant efforts are being devoted to pushing the performances of near-deterministic entangled-photon sources based on single quantum emitters often embedded in photonic cavities, so to boost the flux of photon p… ▽ More The generation of entangled photons from radiative cascades has enabled milestone experiments in quantum information science with several applications in photonic quantum technologies. Significant efforts are being devoted to pushing the performances of near-deterministic entangled-photon sources based on single quantum emitters often embedded in photonic cavities, so to boost the flux of photon pairs. The general postulate is that the emitter generates photons in a nearly maximally entangled state of polarization, ready for application purposes. Here, we demonstrate that this assumption is unjustified. We show that in radiative cascades there exists an interplay between photon polarization and emission wavevector, strongly affecting quantum correlations when emitters are embedded in micro-cavities. We discuss how the polarization entanglement of photon pairs from a biexciton-exciton cascade in quantum dots strongly depends on their propagation wavevector, and it can even vanish for large emission angles. Our experimental results, backed by theoretical modelling, yield a brand-new understanding of cascaded emission for various quantum emitters. In addition, our model provides quantitative guidelines for designing optical microcavities that retain both a high degree of entanglement and collection efficiency, moving the community one step further towards an ideal source of entangled photons for quantum technologies. △ Less

Submitted 12 September, 2024; originally announced September 2024.

Strain-induced dynamic control over the population of quantum emitters in two-dimensional materials

Authors: Giuseppe Ronco, Abel Martínez-Suárez, Davide Tedeschi, Matteo Savaresi, Aurelio Hierro-Rodríguez, Stephen McVitie, Sandra Stroj, Johannes Aberl, Mortiz Brehm, Victor M. García-Suárez, Michele B. Rota, Pablo AlonsoGonzález, Javier Martín-Sánchez, Rinaldo Trotta

Abstract: The discovery of quantum emitters (QEs) in two-dimensional materials (2D) has triggered a surge of research to assess their suitability for quantum photonics. While their microscopic origin is still the subject of intense studies, position-controlled QEs are routinely fabricated using static strain gradients, which are used to drive excitons towards localized regions of the crystal where quantum l… ▽ More The discovery of quantum emitters (QEs) in two-dimensional materials (2D) has triggered a surge of research to assess their suitability for quantum photonics. While their microscopic origin is still the subject of intense studies, position-controlled QEs are routinely fabricated using static strain gradients, which are used to drive excitons towards localized regions of the crystal where quantum light emission takes place. However, the use of strain in a dynamic fashion to control the brightness of single-photon sources in 2D materials has not been explored so far. In this work, we address this challenge by introducing a novel hybrid semiconductorpiezoelectric device in which WSe2 monolayers are integrated onto piezoelectric pillars that provide both static and dynamic strains. The static strains are first used to induce the formation of QEs, whose emission shows photon anti-bunching. Their energy and brightness are then controlled via the application of voltages to the piezoelectric pillars. Numerical simulations combined with drift-diffusion equations show that these effects are due to a strain-induced modification of the confining-potential landscape, which in turn leads to a net redistribution of excitons among the different QEs. Our work provides a method to dynamically control the brightness of single photon sources based on 2D materials. △ Less

Submitted 18 October, 2024; v1 submitted 24 January, 2023; originally announced January 2023.

Comments: 22 pages, 5 figures

A source of entangled photons based on a cavity-enhanced and strain-tuned GaAs quantum dot

Authors: Michele B. Rota, Tobias M. Krieger, Quirin Buchinger, Mattia Beccaceci, Julia Neuwirth, Hêlio Huet, Nikola Horová, Gabriele Lovicu, Giuseppe Ronco, Saimon F. Covre da Silva, Giorgio Pettinari, Magdalena Moczała-Dusanowska, Christoph Kohlberger, Santanu Manna, Sandra Stroj, Julia Freund, Xueyong Yuan, Christian Schneider, Miroslav Ježek, Sven Höfling, Francesco Basso Basset, Tobias Huber-Loyola, Armando Rastelli, Rinaldo Trotta

Abstract: A quantum-light source that delivers photons with a high brightness and a high degree of entanglement is fundamental for the development of efficient entanglement-based quantum-key distribution systems. Among all possible candidates, epitaxial quantum dots are currently emerging as one of the brightest sources of highly entangled photons. However, the optimization of both brightness and entangleme… ▽ More A quantum-light source that delivers photons with a high brightness and a high degree of entanglement is fundamental for the development of efficient entanglement-based quantum-key distribution systems. Among all possible candidates, epitaxial quantum dots are currently emerging as one of the brightest sources of highly entangled photons. However, the optimization of both brightness and entanglement currently requires different technologies that are difficult to combine in a scalable manner. In this work, we overcome this challenge by developing a novel device consisting of a quantum dot embedded in a circular Bragg resonator, in turn, integrated onto a micromachined piezoelectric actuator. The resonator engineers the light-matter interaction to empower extraction efficiencies up to 0.69(4). Simultaneously, the actuator manipulates strain fields that tune the quantum dot for the generation of entangled photons with corrected fidelities to a maximally entangled state up to 0.96(1). This hybrid technology has the potential to overcome the limitations of the key rates that plague QD-based entangled sources for entanglement-based quantum key distribution and entanglement-based quantum networks. △ Less

Submitted 30 April, 2024; v1 submitted 23 December, 2022; originally announced December 2022.

Signatures of the Optical Stark Effect on Entangled Photon Pairs from Resonantly-Pumped Quantum Dots

Authors: Francesco Basso Basset, Michele B. Rota, Mattia Beccaceci, Tobias M. Krieger, Quirin Buchinger, Julia Neuwirth, Hêlio Huet, Sandra Stroj, Saimon F. Covre da Silva, Giuseppe Ronco, Christian Schimpf, Sven Höfling, Tobias Huber-Loyola, Armando Rastelli, Rinaldo Trotta

Abstract: Two-photon resonant excitation of the biexciton-exciton cascade in a quantum dot generates highly polarization-entangled photon pairs in a near-deterministic way. However, the ultimate level of achievable entanglement is still debated. Here, we observe the impact of the laser-induced AC-Stark effect on the quantum dot emission spectra and on entanglement. For increasing pulse-duration/lifetime rat… ▽ More Two-photon resonant excitation of the biexciton-exciton cascade in a quantum dot generates highly polarization-entangled photon pairs in a near-deterministic way. However, the ultimate level of achievable entanglement is still debated. Here, we observe the impact of the laser-induced AC-Stark effect on the quantum dot emission spectra and on entanglement. For increasing pulse-duration/lifetime ratios and pump powers, decreasing values of concurrence are recorded. Nonetheless, additional contributions are still required to fully account for the observed below-unity concurrence. △ Less

Submitted 2 August, 2023; v1 submitted 14 December, 2022; originally announced December 2022.

Comments: The first two authors contributed equally to this work. 8 pages, 4 figures

Journal ref: Phys. Rev. Lett. 131 (2023) 166901

Experimental Multi-state Quantum Discrimination in the Frequency Domain with Quantum Dot Light

Authors: Alessandro Laneve, Michele B. Rota, Francesco Basso Basset, Nicola P. Fiorente, Tobias M. Krieger, Saimon F. Covre da Silva, Quirin Buchinger, Sandra Stroj, Sven Hoefling, Tobias Huber-Loyola, Armando Rastelli, Rinaldo Trotta, Paolo Mataloni

Abstract: The quest for the realization of effective quantum state discrimination strategies is of great interest for quantum information technology, as well as for fundamental studies. Therefore, it is crucial to develop new and more efficient methods to implement discrimination protocols for quantum states. Among the others, single photon implementations are more advisable, because of their inherent secur… ▽ More The quest for the realization of effective quantum state discrimination strategies is of great interest for quantum information technology, as well as for fundamental studies. Therefore, it is crucial to develop new and more efficient methods to implement discrimination protocols for quantum states. Among the others, single photon implementations are more advisable, because of their inherent security advantage in quantum communication scenarios. In this work, we present the experimental realization of a protocol employing a time-multiplexing strategy to optimally discriminate among eight non-orthogonal states, encoded in the four-dimensional Hilbert space spanning both the polarization degree of freedom and photon energy. The experiment, built on a custom-designed bulk optics analyser setup and single photons generated by a nearly deterministic solid-state source, represents a benchmarking example of minimum error discrimination with actual quantum states, requiring only linear optics and two photodetectors to be realized. Our work paves the way for more complex applications and delivers a novel approach towards high-dimensional quantum encoding and decoding operations. △ Less

Submitted 17 September, 2022; originally announced September 2022.

Strain-Tuning of the Optical Properties of Semiconductor Nanomaterials by Integration onto Piezoelectric Actuators

Authors: Javier Martin-Sanchez, Rinaldo Trotta, Antonio Mariscal, Rosalia Serna, Giovanni Piredda, Sandra Stroj, Johannes Edlinger, Christian Schimpf, Johannes Aberl, Thomas Lettner, Johannes Wildmann, Huiying Huang, Xueyong Yuan, Dorian Ziss, Julian Stangl, Armando Rastelli

Abstract: The tailoring of the physical properties of semiconductor nanomaterials by strain has been gaining increasing attention over the last years for a wide range of applications such as electronics, optoelectronics and photonics. The ability to introduce deliberate strain fields with controlled magnitude and in a reversible manner is essential for fundamental studies of novel materials and may lead to… ▽ More The tailoring of the physical properties of semiconductor nanomaterials by strain has been gaining increasing attention over the last years for a wide range of applications such as electronics, optoelectronics and photonics. The ability to introduce deliberate strain fields with controlled magnitude and in a reversible manner is essential for fundamental studies of novel materials and may lead to the realization of advanced multi-functional devices. A prominent approach consists in the integration of active nanomaterials, in thin epitaxial films or embedded within carrier nanomembranes, onto Pb(Mg1/3Nb2/3)O3-PbTiO3-based piezoelectric actuators, which convert electrical signals into mechanical deformation (strain). In this review, we mainly focus on recent advances in strain-tunable properties of self-assembled InAs quantum dots embedded in semiconductor nanomembranes and photonic structures. Additionally, recent works on other nanomaterials like rare-earth and metal-ion doped thin films, graphene and MoS2 or WSe2 semiconductor two-dimensional materials are also reviewed. For the sake of completeness, a comprehensive comparison between different procedures employed throughout the literature to fabricate such hybrid piezoelectric-semiconductor devices is presented. Very recently, a novel class of micro-machined piezoelectric actuators have been demonstrated for a full control of in-plane stress fields in nanomembranes, which enables producing energy-tunable sources of polarization-entangled photons in arbitrary quantum dots. Future research directions and prospects are discussed. △ Less

Submitted 19 October, 2017; originally announced October 2017.

Comments: review manuscript, 78 pages, 27 figures

Journal ref: Semiconductor Science and Technology 33, 013001 (2018)

Reversible Control of In-plane Elastic Stress Tensor in Nanomembranes

Authors: Javier Martín-Sánchez, Rinaldo Trotta, Giovanni Piredda, Christian Schimpf, Giovanna Trevisi, Luca Seravalli, Paola Frigeri, Sandra Stroj, Thomas Lettner, Marcus Reindl, Johannes S. Wildmann, Johannes Edlinger, Armando Rastelli

Abstract: Strain engineering allows the physical properties of materials and devices to be widely tailored, as paradigmatically demonstrated by strained transistors and semiconductor lasers employed in consumer electronics. For this reason, its potential impact on our society has been compared to that of chemical alloying. Although significant progress has been made in the last years on strained nanomateria… ▽ More Strain engineering allows the physical properties of materials and devices to be widely tailored, as paradigmatically demonstrated by strained transistors and semiconductor lasers employed in consumer electronics. For this reason, its potential impact on our society has been compared to that of chemical alloying. Although significant progress has been made in the last years on strained nanomaterials, strain fields (which are of tensorial nature, with six independent components) are still mostly used in a "scalar" and/or static fashion. Here we present a new class of strain actuators which allow the three components of the in-plane stress tensor in a nanomembrane to be independently and reversibly controlled. The actuators are based on monolithic piezoelectric substrates, which are micro-machined via femtosecond-laser processing. Their functionality is demonstrated by "programming" arbitrary stress states in a semiconductor layer, whose light emission is used as a local and sensitive strain gauge. The results shown in this work open a new route to investigate and make use of strain effects in materials and devices. △ Less

Submitted 14 January, 2025; v1 submitted 25 November, 2015; originally announced November 2015.

Comments: 16 pages, 4 figures

Journal ref: Advanced Optical Materials 4(5), 682-687 (2016)

Scalable Sources of Entangled Photons with Wavelength on Demand

Authors: Rinaldo Trotta, Javier Martin-Sanchez, Johannes S. Wildmann, Giovanni Piredda, Marcus Reindl, Christian Schimpf, Eugenio Zallo, Oliver G. Schmidt, Sandra Stroj, Johannes Edlinger, Armando Rastelli

Abstract: The prospect of using the quantum nature of light for secure communication keeps spurring the search and investigation of suitable sources of entangled-photons. Semiconductor quantum dots are arguably the most attractive. They can generate indistinguishable entangled-photons deterministically, and are compatible with current photonic-integration technologies, a set of properties not shared by any… ▽ More The prospect of using the quantum nature of light for secure communication keeps spurring the search and investigation of suitable sources of entangled-photons. Semiconductor quantum dots are arguably the most attractive. They can generate indistinguishable entangled-photons deterministically, and are compatible with current photonic-integration technologies, a set of properties not shared by any other entanglement resource. However, as no two quantum dots are identical, they emit entangled-photons with random energies. This hinders their exploitation in communication protocols requiring entangled-states with well-defined energies. Here, we introduce scalable quantum-dot-based sources of polarization-entangled-photons whose energy can be controlled via dynamic strain-engineering without degrading the degree of entanglement of the source. As a test-bench, we interface quantum dots with clouds of atomic vapours, and we demonstrate slow-entangled-photons from a single quantum emitter. These results pave the way towards the implementation of hybrid quantum networks where entanglement is distributed among distant parties using scalable optoelectronic devices. △ Less

Submitted 23 July, 2015; originally announced July 2015.