| 1. |
- Fognini, A., et al.
(författare)
-
Dephasing Free Photon Entanglement with a Quantum Dot
- 2019
-
Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 6:7, s. 1656-1663
-
Tidskriftsartikel (refereegranskat)abstract
- Generation of photon pairs from quantum dots with near-unity entanglement fidelity has been a long-standing scientific challenge. It is generally thought that the nuclear spins limit the entanglement fidelity through spin flip dephasing processes. However, this assumption lacks experimental support. Here, we show two-photon entanglement with negligible dephasing from an indium rich single quantum dot comprising a nuclear spin of 9/2 when excited quasi-resonantly. This finding is based on a significantly close match between our entanglement measurements and our model that assumes no dephasing and takes into account the detection system's timing jitter and dark counts. We suggest that neglecting the detection system is responsible for the degradation of the measured entanglement fidelity in the past and not the nuclear spins. Therefore, the key to unity entanglement from quantum dots comprises a resonant excitation scheme and a detection system with ultralow timing jitter and dark counts.
|
|
| 2. |
- Zadeh, I. E., et al.
(författare)
-
Scalable quantum optics with nanowires
- 2019
-
Ingår i: Optics InfoBase Conference Papers. - : OSA - The Optical Society. - 9781943580569
-
Konferensbidrag (refereegranskat)abstract
- Single-photon generation, processing, and detection are the three main components of any quantum optical circuit. We present our results on integration of semiconducting nanowire quantum dots, dielectric waveguides, and ultrahigh performance superconducting nanowire single-photon detectors.
|
|
| 3. |
- Lagoudakis, K. G., et al.
(författare)
-
Ultrafast coherent manipulation of trions in site-controlled nanowire quantum dots
- 2016
-
Ingår i: Optica. - : Optical Society of America. - 2334-2536. ; 3:12, s. 1430-1435
-
Tidskriftsartikel (refereegranskat)abstract
- Physical implementations of large-scale quantum processors based on solid-state platforms benefit from realizations of quantum bits positioned in regular arrays. Self-assembled quantum dots are well established as promising candidates for quantum optics and quantum information processing, but they are randomly positioned. Site-controlled quantum dots, on the other hand, are grown in pre-defined locations but have not yet been sufficiently developed to be used as a platform for quantum information processing. In this paper, we demonstrate all-optical ultrafast complete coherent control of a qubit formed by the single-spin/trion states of a charged site-controlled nanowire quantum dot. Our results show that site-controlled quantum dots in nanowires are promising hosts of charged-exciton qubits and that these qubits can be cleanly manipulated in the same fashion as has been demonstrated in randomly positioned quantum dot samples. Our findings suggest that many of the related excitonic qubit experiments that have been performed over the past 15 years may work well in the more scalable, site-controlled systems, making them very promising for the realization of quantum hardware.
|
|
| 4. |
- Brodu, Annalisa, et al.
(författare)
-
Exciton Fine Structure and Lattice Dynamics in InP/ZnSe Core/Shell Quantum Dots
- 2018
-
Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 5:8, s. 3353-3362
-
Tidskriftsartikel (refereegranskat)abstract
- Nanocrystalline InP quantum dots (QDs) hold promise for heavy-metal-free optoelectronic applications due to their bright and size tunable emission in the visible range. Photochemical stability and high photoluminescence (PL) quantum yield are obtained by a diversity of epitaxial shells around the InP core. To understand and optimize the emission line shapes, the exciton fine structure of InP core/shell QD systems needs be investigated. Here, we study the exciton fine structure of InP/ZnSe core/shell QDs with core diameters ranging from 2.9 to 3.6 nm (PL peak from 2.3 to 1.95 eV at 4 K). PL decay measurements as a function of temperature in the 10 mK to 300 K range show that the lowest exciton fine structure state is a dark state, from which radiative recombination is assisted by coupling to confined acoustic phonons with energies ranging from 4 to 7 meV, depending on the core diameter. Circularly polarized fluorescence line-narrowing (FLN) spectroscopy at 4 K under high magnetic fields (up to 30 T) demonstrates that radiative recombination from the dark F = +/- 2 state involves acoustic and optical phonons, from both the InP core and the ZnSe shell. Our data indicate that the highest intensity FLN peak is an acoustic phonon replica rather than a zero-phonon line, implying that the energy separation observed between the F = +/- 1 state and the highest intensity peak in the FLN spectra (6 to 16 meV, depending on the InP core size) is larger than the splitting between the dark and bright fine structure exciton states.
|
|
| 5. |
- Elshaari, Ali W., et al.
(författare)
-
Hybrid quantum photonic integrated circuits
- 2018
-
Ingår i: Proceedings - International Conference Laser Optics 2018, ICLO 2018. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538636121
-
Konferensbidrag (refereegranskat)abstract
- Quantum photonic integrated circuits require a scalable approach to integrate bright on-demand sources of entangled photon-pairs in complex on-chip quantum photonic circuits. Currently, the most promising sources are based on III/V semiconductor quantum dots. However, complex photonic circuitry is mainly achieved in silicon photonics due to the tremendous technological challenges in circuit fabrication. We take the best of both worlds by developing a new hybrid on-chip nanofabrication approach, allowing to integrate III/V semiconductor nanowire quantum emitters into silicon-based photonics.
|
|
| 6. |
- Elshaari, Ali W., et al.
(författare)
-
Hybrid quantum photonics
- 2017
-
Ingår i: Optics InfoBase Conference Papers. - : Optical Society of America. - 9781943580279
-
Konferensbidrag (refereegranskat)abstract
- We deterministically integrate nanowire quantum-emitters in SiN photonic circuits. We generate single-photons, suppress excitation-laser, and isolate specific transitions in the quantumemitter all on-chip with electrically-tunable filter. Finally, we demonstrate a novel Quantum- WDM channel on-chip.
|
|
| 7. |
- Elshaari, Ali W., et al.
(författare)
-
On-chip single photon filtering and multiplexing in hybrid quantum photonic circuits
- 2017
-
Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- Quantum light plays a pivotal role in modern science and future photonic applications. Since the advent of integrated quantum nanophotonics different material platforms based on III-V nanostructures-, colour centers-, and nonlinear waveguides as on-chip light sources have been investigated. Each platform has unique advantages and limitations; however, all implementations face major challenges with filtering of individual quantum states, scalable integration, deterministic multiplexing of selected quantum emitters, and on-chip excitation suppression. Here we overcome all of these challenges with a hybrid and scalable approach, where single III-V quantum emitters are positioned and deterministically integrated in a complementary metal-oxide-semiconductor-compatible photonic circuit. We demonstrate reconfigurable on-chip single-photon filtering and wavelength division multiplexing with a foot print one million times smaller than similar table-top approaches, while offering excitation suppression of more than 95 dB and efficient routing of single photons over a bandwidth of 40 nm. Our work marks an important step to harvest quantum optical technologies' full potential.
|
|
| 8. |
- Elshaari, Ali W., et al.
(författare)
-
Strain-Tunable Quantum Integrated Photonics
- 2018
-
Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 18:12, s. 7969-7976
-
Tidskriftsartikel (refereegranskat)abstract
- Semiconductor quantum dots are crucial parts of the photonic quantum technology toolbox because they show excellent single-photon emission properties in addition to their potential as solid-state qubits. Recently, there has been an increasing effort to deterministically integrate single semiconductor quantum dots into complex photonic circuits. Despite rapid progress in the field, it remains challenging to manipulate the optical properties of waveguide-integrated quantum emitters in a deterministic, reversible, and nonintrusive manner. Here we demonstrate a new class of hybrid quantum photonic circuits combining III V semiconductors, silicon nitride, and piezoelectric crystals. Using a combination of bottom-up, top-down, and nanomanipulation techniques, we realize strain tuning of a selected, waveguide-integrated, quantum emitter and a planar integrated optical resonator. Our findings are an important step toward realizing reconfigurable quantum-integrated photonics, with full control over the quantum sources and the photonic circuit.
|
|
| 9. |
- Fognini, A., et al.
(författare)
-
Universal fine-structure eraser for quantum dots
- 2018
-
Ingår i: Optics Express. - : OPTICAL SOC AMER. - 1094-4087. ; 26:19, s. 24487-24496
-
Tidskriftsartikel (refereegranskat)abstract
- We analyze the degree of entanglement measurable from a quantum dot via the biexciton-exciton cascade as a function of the exciton fine-structure splitting and the detection time resolution. We show that the time-energy uncertainty relation provides means to measure a high entanglement even in presence of a finite fine-structure splitting when a detection system with high temporal resolution is employed. Still, in many applications it would be beneficial if the fine-structure splitting could be compensated to zero. To solve this problem, we propose an all-optical approach with rotating waveplates to erase this fine-structure splitting completely which should allow obtaining a high degree of entanglement with near-unity efficiency. Our optical approach is possible with current technology and is also compatible with any quantum dot showing fine-structure splitting. This bears the advantage that for example the fine-structure splitting of quantum dots in nanowires and micropillars can be directly compensated without the need for further sample processing.
|
|
| 10. |
- Gourgues, Ronan, et al.
(författare)
-
Controlled integration of selected detectors and emitters in photonic integrated circuits
- 2019
-
Ingår i: Optics Express. - : OPTICAL SOC AMER. - 1094-4087. ; 27:3, s. 3710-3716
-
Tidskriftsartikel (refereegranskat)abstract
- Integration of superconducting nanowire single-photon detectors and quantum sources with photonic waveguides is crucial for realizing advanced quantum integrated circuits. However, scalability is hindered by stringent requirements on high-performance detectors. Here we overcome the yield limitation by controlled coupling of photonic channels to pre-selected detectors based on measuring critical current, timing resolution, and detection efficiency. As a proof of concept of our approach, we demonstrate a hybrid on-chip full-transceiver consisting of a deterministically integrated detector coupled to a selected nanowire quantum dot through a filtering circuit made of a silicon nitride waveguide and a ring resonator filter, delivering 100 dB suppression of the excitation laser. In addition, we perform extensive testing of the detectors before and after integration in the photonic circuit and show that the high performance of the superconducting nanowire detectors, including timing jitter down to 23 +/- 3 ps, is maintained. Our approach is fully compatible with wafer-level automated testing in a cleanroom environment.
|
|
