| 11. |
- Li, Qian, et al.
(författare)
-
Using electric fields for pulse compression and group-velocity control
- 2017
-
Ingår i: Physical Review A. - 2469-9926. ; 95:3
-
Tidskriftsartikel (refereegranskat)abstract
- In this article, we experimentally demonstrate a way of controlling the group velocity of an optical pulse by using a combination of spectral hole burning, the slow-light effect, and the linear Stark effect in a rare-earth-ion-doped crystal. The group velocity can be changed continuously by a factor of 20 without significant pulse distortion or absorption of the pulse energy. With a similar technique, an optical pulse can also be compressed in time. Theoretical simulations were developed to simulate the group-velocity control and the pulse compression processes. The group velocity as well as the pulse reshaping are solely controlled by external voltages which makes it promising in quantum information and quantum communication processes. It is also proposed that the group velocity can be changed even more in an Er-doped crystal while at the same time having a transmission band matching the telecommunication wavelength.
|
|
| 12. |
- Serrano, Diana, et al.
(författare)
-
Satellite line mapping in Eu3+-Ce3+ and Pr3+-Ce3+ codoped Y2SiO5
- 2016
-
Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 170, s. 102-107
-
Tidskriftsartikel (refereegranskat)abstract
- In this work we perform a high-resolution spectroscopic investigation of Eu3+-Ce3+ and Pr3+-Ce3+ codoped Y2SiO5 crystals. Satellite line spectra were recorded at low temperatures around the Eu3+:F-7(0) -> D-5(0) and the Pr3+:H-3(4) -> D-1(2) transitions. It is observed that the incorporation of Ce3+ as a codopant notably changes the Eu3+ and Pr3+ satellite line patterns. Satellite lines measured in singly doped Eu3+:Y2SiO5 were found at the same spectral positions in Eu3+-Ce3+ codoped crystals. These coincident lines were concluded to be due to pairs of Eu3+ ions. Extra satellite lines appeared in the codoped crystals, which were assigned to Ce3+ related structures such as Ce3+-Eu3+ pairs. The analysis of the Pr3+ satellite line spectra presents further challenges. Satellite lines associated to Pr3+ pairs show weaker intensity, presumably due to the efficient quenching of the Pr3+ D-1(2) emission through cross-relaxation paths (D-1(2) -> (1)G(4); H-3(4) -> F-3(4)). The investigation of the Eu3+ and Pr3+ satellite line patterns in Y2SiO5 is particularly interesting for their exploitation in rare-earth based quantum computation schemes. (C) 2015 Elsevier B.V. All rights reserved.
|
|
| 13. |
- Walther, Andreas, et al.
(författare)
-
Fast all-optical nuclear spin echo technique based on EIT
- 2016
-
Ingår i: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060. ; 70:8
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract: We demonstrate an all-optical Raman spin echo technique, using electromagneticallyinduced transparency (EIT) to create the pulses required for a spin echo sequence:initialization, pi-rotation, and readout. The first pulse of the sequence inducescoherence directly from a mixed state, and the technique is used to measure the nuclearspin coherence of an inhomogeneously broadened ensemble of rare-earth ions(Pr3 +) in acrystal. The rephasing pi-rotation is shown to offer an advantage of combining therephasing action with the operation of a phase gate, particularly useful in e.g. dynamicdecoupling sequences. In contrast to many previous experiments the sequence does notrequire any preparatory hole burning, which greatly shortens the total duration of thesequence. The effect of the different pulses is characterized by quantum state tomographyand compared with simulations. We demonstrate two applications of the technique:compensating the magnetic field across our sample by monitoring T2 reductionsfrom stray magnetic fields, and measuring coherence times at temperatures up to 11 K,where standard preparation techniques are difficult to implement. We explore the potentialof the technique, in particular for systems with much shorter T2, and otherpossible applications. Graphical abstract: [Figure not available: see fulltext.]
|
|
| 14. |
- Walther, Andreas, et al.
(författare)
-
High-fidelity readout scheme for rare-earth solid-state quantum computing
- 2015
-
Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 92:2
-
Tidskriftsartikel (refereegranskat)abstract
- We propose and analyze a high-fidelity readout scheme for a single-instance approach to quantum computing in rare-earth-ion-doped crystals. The scheme is based on using different elements as qubit and readout ions, where the readout ions are doped into the material at a much lower concentration than the qubit ions. It is shown that by allowing the qubit ion sitting closest to a readout ion to act as a readout buffer, the readout error can be reduced by more than an order of magnitude. The scheme is shown to be robust against certain experimental variations, such as varying detection efficiencies, and we use the scheme to predict the attainable quantum fidelity of a controlled NOT (CNOT) gate in these solid-state systems. In addition, we discuss the potential scalability of the protocol to larger qubit systems. The results are based on parameters which we believe are experimentally feasible with current technology and which can be simultaneously realized.
|
|
| 15. |
- Yan, Ying, et al.
(författare)
-
Inverse engineering of shortcut pulses for high fidelity initialization on qubits closely spaced in frequency
- 2019
-
Ingår i: Optics Express. - 1094-4087. ; 27:6, s. 8267-8282
-
Tidskriftsartikel (refereegranskat)abstract
- High-fidelity qubit initialization is of significance for efficient error correction in fault tolerant quantum algorithms. Combining two best worlds, speed and robustness, to achieve high-fidelity state preparation and manipulation is challenging in quantum systems, where qubits are closely spaced in frequency. Motivated by the concept of shortcut to adiabaticity, we theoretically propose the shortcut pulses via inverse engineering and further optimize the pulses with respect to systematic errors in frequency detuning and Rabi frequency. Such protocol, relevant to frequency selectivity, is applied to rare-earth ions qubit system, where the excitation of frequency-neighboring qubits should be prevented as well. Furthermore, comparison with adiabatic complex hyperbolic secant pulses shows that these dedicated initialization pulses can reduce the time that ions spend in the excited state by a factor of 6, which is important in coherence time limited systems to approach an error rate manageable by quantum error correction. The approach may also be applicable to superconducting qubits, and any other systems where qubits are addressed in frequency.
|
|
