| 1. |
- Fognini, A., et al.
(författare)
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Dephasing Free Photon Entanglement with a Quantum Dot
- 2019
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Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 6:7, s. 1656-1663
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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.
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| 2. |
- Barthelmi, K., et al.
(författare)
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Atomistic defects as single-photon emitters in atomically thin MoS2
- 2020
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 117:7
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Tidskriftsartikel (refereegranskat)abstract
- Precisely positioned and scalable single-photon emitters (SPEs) are highly desirable for applications in quantum technology. This Perspective discusses single-photon-emitting atomistic defects in monolayers of MoS2 that can be generated by focused He-ion irradiation with few nanometers positioning accuracy. We present the optical properties of the emitters and the possibilities to implement them into photonic and optoelectronic devices. We showcase the advantages of the presented emitters with respect to atomistic positioning, scalability, long (microsecond) lifetime, and a homogeneous emission energy within ensembles of the emitters. Moreover, we demonstrate that the emitters are stable in energy on a timescale exceeding several weeks and that temperature cycling narrows the ensembles' emission energy distribution.
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| 3. |
- Chang, J., et al.
(författare)
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Detecting telecom single photons with (99.5(-2.07)(+0.5))% system detection efficiency and high time resolution
- 2021
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Ingår i: APL Photonics. - : AIP Publishing. - 2378-0967. ; 6:3
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Tidskriftsartikel (refereegranskat)abstract
- Single photon detectors are indispensable tools in optics, from fundamental measurements to quantum information processing. The ability of superconducting nanowire single photon detectors (SNSPDs) to detect single photons with unprecedented efficiency, short dead time, and high time resolution over a large frequency range enabled major advances in quantum optics. However, combining near-unity system detection efficiency (SDE) with high timing performance remains an outstanding challenge. In this work, we fabricated novel SNSPDs on membranes with 99.5-(2.07)(+0.5)% SDE at 1350 nm with 32 ps timing jitter (using a room-temperature amplifier), and other detectors in the same batch showed 94%-98% SDE at 1260-1625 nm with 15-26 ps timing jitter (using cryogenic amplifiers). The SiO2/Au membrane enables broadband absorption in small SNSPDs, offering high detection efficiency in combination with high timing performance. With low-noise cryogenic amplifiers operated in the same cryostat, our efficient detectors reach a timing jitter in the range of 15-26 ps. We discuss the prime challenges in optical design, device fabrication, and accurate and reliable detection efficiency measurements to achieve high performance single photon detection. As a result, the fast developing fields of quantum information science, quantum metrology, infrared imaging, and quantum networks will greatly benefit from this far-reaching quantum detection technology.
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| 4. |
- Zadeh, I. E., et al.
(författare)
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Scalable quantum optics with nanowires
- 2019
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Ingår i: Optics InfoBase Conference Papers. - : OSA - The Optical Society. - 9781943580569
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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.
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| 5. |
- Barnes, W. L., et al.
(författare)
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Solid-state single photon sources : light collection strategies
- 2002
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Ingår i: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 18:2, s. 197-210
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Tidskriftsartikel (refereegranskat)abstract
- We examine the problem of efficiently collecting the photons produced by solid-state single photon sources. The extent of the problem is first established with the aid of simple physical concepts. Several approaches to improving the collection efficiency are then examined and are broadly categorized into two types. First are those based on cavity quantum dynamics, in which the pathways by which the source may emit a photon are restricted, thus channeling emission into one desired mode. Second are those where we try to reshape the free space modes into a target mode in an optimal way, by means of refraction, without fundamentally altering the way in which the source emits. Respectively, we examine a variety of microcavities and solid immersion lenses. Whilst we find that the micropillar microcavities offer the highest collection efficiency (similar to70%), choosing this approach may not always be appropriate due to other constraints. Details of the different approaches, their merits and drawbacks are discussed in detail.
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| 6. |
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| 7. |
- Lagoudakis, K. G., et al.
(författare)
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Ultrafast coherent manipulation of trions in site-controlled nanowire quantum dots
- 2016
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Ingår i: Optica. - : Optical Society of America. - 2334-2536. ; 3:12, s. 1430-1435
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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.
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| 8. |
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| 9. |
- Zadeh, Iman Esmaeil, et al.
(författare)
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Efficient Single-Photon Detection with 7.7 ps Time Resolution for Photon-Correlation Measurements
- 2020
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Ingår i: ACS Photonics. - : AMER CHEMICAL SOC. - 2330-4022. ; 7:7, s. 1780-1787
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Tidskriftsartikel (refereegranskat)abstract
- A broad range of scientific and industrial disciplines require precise optical measurements at very low light levels. Single-photon detectors combining high efficiency and high time resolution are pivotal in such experiments. By using relatively thick films of NbTiN (8-11 nm) and improving the pattern fidelity of the nanostructure of the superconducting nanowire single-photon detectors (SNSPD), we fabricated devices demonstrating superior performance over all previously reported detectors in the combination of efficiency and time resolution. Our findings prove that small variations in the nanowire width, in the order of a few nanometers, can lead to a significant penalty on their temporal response. Addressing these issues, we consistently achieved high time resolution (best device 7.7 ps, other devices similar to 10-16 ps) simultaneously with high system detection efficiencies (80-90%) in the wavelength range of 780-1000 nm, as well as in the telecom bands (1310-1550 nm). The use of thicker films allowed us to fabricate large-area multipixel devices with homogeneous pixel performance. We first fabricated and characterized a 100 x 100 mu m(2) 16-pixel detector and showed there was little variation among individual pixels. Additionally, to showcase the power of our platform, we fabricated and characterized 4-pixel multimode fiber-coupled detectors and carried out photon-correlation experiments on a nanowire quantum dot resulting in g(2) (0) values lower than 0.04. The multipixel detectors alleviate the need for beamsplitters and can be used for higher order correlations with promising prospects not only in the field of quantum optics, but also in bioimaging applications, such as fluorescence microscopy and positron emission tomography.
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| 10. |
- Bienfang, J. C., et al.
(författare)
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Materials, devices, and systems for high-speed single-photon counting
- 2022
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Ingår i: MRS bulletin. - : Springer Nature. - 0883-7694 .- 1938-1425. ; 47:5, s. 494-501
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Tidskriftsartikel (refereegranskat)abstract
- Optical communications and high-speed optoelectronics are enabling technologies for modern information networks. Driven by the need for improved bandwidth, high efficiency, and low noise, advances over the last decades have led to high-performance photodetectors operating at the quantum limit. In particular, single-photon avalanche diodes (SPADs) and superconducting nanowire single-photon detectors (SNSPDs) provide excellent performance in terms of high detection efficiency and low noise. In this article, we highlight materials challenges in these detectors and review recent progress on devices, and systems for high-count-rate single-photon counting with SPADs and SNSPDs. Device configurations specifically designed for high-speed optoelectronics are discussed, including active detector readout schemes. Advantages and tradeoffs of the different device technologies are summarized and compared, providing an outlook on future prospects for performance optimization and emerging applications.
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