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- ItemFirst Terahertz-range Experiments on Pump – Probe Setup at Novosibirsk free Electron Laser(Amsterdam [u.a.] : Elsevier, 2016) Choporova, Yulia Yu.; Gerasimov, Vasily V.; Knyazev, Boris A.; Sergeev, Sergey M.; Shevchenko, Oleg A.; Zhukavin, Roman K.; Abrosimov, Nikolay V.; Kovalevsky, Konstantin A.; Ovchar, Vladimir K.; Hübers, Heinz-Wilhelm; Kulipanov, Gennady N.; Shastin, Valery N.; Schneider, Harald; Vinokurov, Nikolay A.A single-color pump-probe system has been commissioned at the Novosibirsk free electron laser. The laser emits a tunable monochromatic terahertz radiation. To prove the proper system operation, we investigated the time-resolved absorption of a sample of n-type germanium doped with antimony, which was previously investigated at the FELBE facility, in the temperature range from 5 to 40 K. The measured relaxation time amounted to about 1.7 ns, which agreed with the results obtained at the FELBE. The results of pump-probe measurements of non-equilibrium dynamics of hot electrons in the germanium crystal at cryogenic temperatures are presented for wavelengths of 105, 141 and 150 μm.
- ItemCharacterization of the Si:Se+ Spin-Photon Interface(College Park, Md. [u.a.] : American Physical Society, 2019) DeAbreu, Adam; Bowness, Camille; Abraham, Rohan J.S.; Medvedova, Alzbeta; Morse, Kevin J.; Riemann, Helge; Abrosimov, Nikolay V.; Becker, Peter; Pohl, Hans-Joachim; Thewalt, Michael L.W.; Simmons, StephanieSilicon is the most-developed electronic and photonic technological platform and hosts some of the highest-performance spin and photonic qubits developed to date. A hybrid quantum technology harnessing an efficient spin-photon interface in silicon would unlock considerable potential by enabling ultralong-lived photonic memories, distributed quantum networks, microwave-to-optical photon converters, and spin-based quantum processors, all linked with integrated silicon photonics. However, the indirect band gap of silicon makes identification of efficient spin-photon interfaces nontrivial. Here we build upon the recent identification of chalcogen donors as a promising spin-photon interface in silicon. We determine that the spin-dependent optical degree of freedom has a transition dipole moment stronger than previously thought [here 1.96(8) D], and the spin T1 lifetime in low magnetic fields is longer than previously thought [here longer than 4.6(1.5) h]. We furthermore determine the optical excited-state lifetime [7.7(4) ns], and therefore the natural radiative efficiency [0.80(9)%], and by measuring the phonon sideband determine the zero-phonon emission fraction [16(1)%]. Taken together, these parameters indicate that an integrated quantum optoelectronic platform based on chalcogen-donor qubits in silicon is well within reach of current capabilities.
- ItemAuthor Correction: Low-frequency spin qubit energy splitting noise in highly purified 28Si/SiGe (npj Quantum Information, (2020), 6, 1, (40), 10.1038/s41534-020-0276-2)(London : Nature Publ. Group, 2020) Struck, Tom; Hollmann, Arne; Schauer, Floyd; Fedorets, Olexiy; Schmidbauer, Andreas; Sawano, Kentarou; Riemann, Helge; Abrosimov, Nikolay V.; Cywiński, Łukasz; Bougeard, Dominique; Schreiber, Lars R.The original version of this Article omitted the following from the Acknowledgements: “This work has also been funded by the National Science Centre, Poland under QuantERA program, Grant No. 2017/25/Z/ST3/03044.” This has now been corrected in both the PDF and HTML versions of the Article. © 2020, The Author(s).
- ItemLow-frequency spin qubit energy splitting noise in highly purified 28Si/SiGe(London : Nature Publ. Group, 2020) Struck, Tom; Hollmann, Arne; Schauer, Floyd; Fedorets, Olexiy; Schmidbauer, Andreas; Sawano, Kentarou; Riemann, Helge; Abrosimov, Nikolay V.; Cywiński, Łukasz; Bougeard, Dominique; Schreiber, Lars R.We identify the dominant source for low-frequency spin qubit splitting noise in a highly isotopically-purified silicon device with an embedded nanomagnet and a spin echo decay time T2echo = 128 µs. The power spectral density (PSD) of the charge noise explains both, the clear transition from a 1/f2- to a 1/f-dependence of the splitting noise PSD as well as the experimental observation of a decreasing time-ensemble spin dephasing time, from T2*˜ 20 µs, with increasing measurement time over several hours. Despite their strong hyperfine contact interaction, the few 73Ge nuclei overlapping with the quantum dot in the barrier do not limit T2*, likely because their dynamics is frozen on a few hours measurement scale. We conclude that charge noise and the design of the gradient magnetic field are the key to further improve the qubit fidelity in isotopically purified 28Si/SiGe. © 2020, The Author(s).
- ItemA photonic platform for donor spin qubits in silicon(Washington, DC [u.a.] : Assoc., 2017) Morse, Kevin J.; Abraham, Rohan J. S.; DeAbreu, Adam; Bowness, Camille; Richards, Timothy S.; Riemann, Helge; Abrosimov, Nikolay V.; Becker, Peter; Pohl, Hans-Joachim; Thewalt, Michael L. W.; Simmons, StephanieDonor spins in silicon are highly competitive qubits for upcoming quantum technologies, offering complementary metal-oxide semiconductor compatibility, coherence (T2) times of minutes to hours, and simultaneous initialization, manipulation, and readout fidelities near ~99.9%. This allows for many quantum error correction protocols, which will be essential for scale-up. However, a proven method of reliably coupling spatially separated donor qubits has yet to be identified. We present a scalable silicon-based platform using the unique optical properties of “deep” chalcogen donors. For the prototypical 77Se+ donor, we measure lower bounds on the transition dipole moment and excited-state lifetime, enabling access to the strong coupling limit of cavity quantum electrodynamics using known silicon photonic resonator technology and integrated silicon photonics. We also report relatively strong photon emission from this same transition. These results unlock clear pathways for silicon-based quantum computing, spin-to-photon conversion, photonic memories, integrated single-photon sources, and all-optical switches.