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Research Highlights.
 

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Advanced Optical Materials 7, 2021
Inside Cover

The cover design of the article Bright Single Photon Emission from Quantum Dots Embedded in a Broadband Planar Optical Antenna, opens an external URL in a new window by H. Huang, S. Manna, C. Schimpf, M. Reindl, X. Yuan, Y. Zhang, S. Covre da Silva and A. Rastelli (Adv. Optical Mater. 2001490, 2021) has been featured on the inside cover of the issue of "Advanced Optical Materials" 7, 2021.

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F. Basso Basset, F. Salusti, L. Schweickert, M. Rota, D. Tedeschi, S. Filipe Covre da Silva, E. Roccia, V. Zwiller, K. Jöns, A. Rastelli, R. Trotta

Quantum teleportation with imperfect quantum dots, opens an external URL in a new window

npj Quantum Information 7 (2021)

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E. A. Chekhovich, S. Filipe Covre da Silva, A. Rastelli

Nuclear spin quantum register in an optically active semiconductor quantum dot, opens an external URL in a new window

Nature Nanotechnology 15, 999-1004 (2020).

Epitaxial quantum dots (QDs) have long been identified as promising charge spin qubits offering an efficient interface to quantum light and advanced semiconductor nanofabrication technologies. However, charge spin coherence is limited by interaction with the nanoscale ensemble of atomic nuclear spins, which is particularly problematic in strained self-assembled dots. Here, we use strain-free GaAs/AlGaAs QDs, demonstrating a fully functioning two-qubit quantum register using the nanoscale ensemble of arsenic quadrupolar nuclear spins as its hardware. Tailored radio-frequency pulses allow quantum state storage for up to 20 ms, and are used for few-microsecond single-qubit and two-qubit control gates with fidelities exceeding 97%. Combining long coherence and high-fidelity control with optical initialization and readout, we implement benchmark quantum computations such as Grover’s search and the Deutsch–Jozsa algorithm. Our results identify QD nuclei as a potential quantum information resource, which can complement charge spins and light particles in future QD circuits.

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J.Liu, R. Su, Y. Wei, B. Yao, S. F. Covre da Silva, Y. Yu, J. Iles-Smith, K. Srinivasan, A. Rastelli, J. Li, X. Wang

A solid-state source of strongly entangled photon pairs with high brightness and indistinguishability, opens an external URL in a new window

Nature Nanotechnology 14, 586–593 (2019).

©Toan T. Tran (https://www.nature.com/articles/s41565-019-0440-z/figures/1)

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Breakthrough in Quantum Teleportation on Demand

M.Reindl, D. Huber, C. Schimpf, S. Filipe Covre da Silva, M. Rota, H. Huang, V. Zwiller, K. Jöns, A. Rastelli, R. Trotta   

All-photonic quantum teleportation using on-demand solid-state quantum emitters, opens an external URL in a new window

Sci. Adv. 4, eaau1255 (2018).

All-optical quantum teleportation lies at the heart of quantum communication science and technology. This quantum phenomenon is built up around the nonlocal properties of entangled states of light that, in the perspective of real-life applications, should be encoded on photon pairs generated on demand. Despite recent advances, however, the exploitation of deterministic quantum light sources in push-button quantum teleportation schemes remains a major open challenge. Here, we perform an important step toward this goal and show that photon pairs generated on demand by a GaAs quantum dot can be used to implement a teleportation protocol whose fidelity violates the classical limit (by more than 5 SDs) for arbitrary input states. Moreover, we develop a theoretical framework that matches the experimental observations and that defines the degree of entanglement and indistinguishability needed to overcome the classical limit independently of the input state. Our results emphasize that on-demand solid-state quantum emitters are one of the most promising candidates to realize deterministic quantum teleportation in practical quantum networks.

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Xueyong Yuan, Fritz Weyhausen-Brinkmann, Javier Martín-Sánchez, Giovanni Piredda, Vlastimil Křápek, Yongheng Huo, Huiying Huang, Christian Schimpf, Oliver G. Schmidt, Johannes Edlinger, Gabriel Bester, Rinaldo Trotta, Armando Rastelli

Uniaxial stress flips the natural quantization axis of a quantum dot for integrated quantum photonics

Nature Communications 9, 3058 (2018), opens an external URL in a new window

By using a novel piezoelectric actuator featuring geometric strain amplification, we have demonstrated that the natural quantization axis of strain-free GaAs quantum dots can be flipped to lie in the growth plane via moderate uniaxial stress. Together with the computational results, our work illustrate that uniaxial stress could be the right method to obtain quantum-light sources with ideally oriented transition dipoles and enhanced oscillator strengths for integrated quantum photonics.

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Daniel Huber, Marcus Reindl, Saimon Filipe Covre da Silva, Christian Schimpf, Javier Martín-Sánchez, Huiying Huang, Giovanni Piredda, Johannes Edlinger, Armando Rastelli, and Rinaldo Trotta:

Strain-Tunable GaAs Quantum Dot: A Nearly Dephasing-Free Source of Entangled Photon Pairs on Demand

Phys. Rev. Lett. 121, 033902 (2018)., opens an external URL in a new window

Entangled photon pairs are a key resource for quantum communication. We have now achieved the highest degree of polarization entanglement for photon pairs emitted by quantum dots by combining: 1) High-quality GaAs quantum dots grown by molecular beam epitaxy at our institute and embedded in planar cavities for enhanced light extraction, 2) resonant two-photon excitation for on demand operation, and 3) micro-structured piezoelectric actuators for removing the effect of residual anisotropy in the quantum dot potential. This work shows that quantum dots have the potential to fulfill the criteria of a perfect entangled-photon source.

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L. Schweickert, K. D. Jöns, K. D. Zeuner, S. F. Covre da Silva, H. Huang, T. Lettner, M. Reindl, J. Zichi, R. Trotta, A. Rastelli, V. Zwiller:


On-demand generation of background-free single photons from a solid-state source


Appl. Phys. Lett. 112, 093106 (2018), opens an external URL in a new window

Our collaborators at KTH Stockholm demonstrated an unprecedented single photon purity in the solid-state which exceeds the performance of any available single photon source to date. The used quantum dot source was grown in Linz.

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