An idea for how to reconstruct the quantum state of a nonstationary single-photon wave packet absorbed in a macroscopic medium with inhomogeneously broadened lines is presented. An analytical ...treatment of the problem is performed and the requirements on the proposed scheme for complete recovery of the recorded nonstationary quantum state with a probability close to unity is described. The physical nature of the present scheme is also discussed.
Quantum memories Simon, C.; Afzelius, M.; Appel, J. ...
The European physical journal. D, Atomic, molecular, and optical physics,
2010/5, Letnik:
58, Številka:
1
Journal Article
Recenzirano
We perform a review of various approaches to the implementation of quantum memories, with an emphasis on activities within the quantum memory sub-project of the EU integrated project “Qubit ...Applications”. We begin with a brief overview over different applications for quantum memories and different types of quantum memories. We discuss the most important criteria for assessing quantum memory performance and the most important physical requirements. Then we review the different approaches represented in “Qubit Applications” in some detail. They include solid-state atomic ensembles, NV centers, quantum dots, single atoms, atomic gases and optical phonons in diamond. We compare the different approaches using the discussed criteria.
Towards an efficient atomic frequency comb quantum memory Amari, A.; Walther, A.; Sabooni, M. ...
10th International Meeting on Hole Burning, Single Molecule and Related Spectroscopies,2009-06-22 - 2009-06-27,
09/2010, Letnik:
130, Številka:
9
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
We present an efficient photon-echo experiment based on atomic frequency combs Phys. Rev. A 79 (2009) 052329. Echoes containing an energy of up to 35% of that of the input pulse are observed in a Pr
...3+-doped Y
2SiO
5 crystal. This material allows for the precise spectral holeburning needed to make a sharp and highly absorbing comb structure. We compare our results with a simple theoretical model with satisfactory agreement. Our results show that atomic frequency combs has the potential for high-efficiency storage of single photons as required in future long-distance communication based on quantum repeaters.
We analyze the Ce3+–Pr3+:Y2SiO5 emission spectra obtained under selective excitation of the two Ce3+ sites in Y2SiO5 and we show clear evidence of direct energy transfer from Ce3+ to Pr3+. Energy ...transfer microparameters were calculated from the experimental spectral overlap between the Ce3+ emission and the Pr3+ and Eu3+ absorptions from which, the transfer mechanisms Ce3+→Pr3+ are concluded to be more efficient than the transfer mechanisms Ce3+→Eu3+. The energy transfer processes demonstrated here are potentially detrimental for an efficient qubit readout, using Ce3+ as readout ion, as they lead to a quenching of the Ce3+ luminescence and can give rise to the unwanted change of Pr3+ and Eu3+ qubit states. The quantum computing readout scheme is based on permanent electric dipole interactions scaling as R−3, where R is the distance between the Ce3+ and the qubit ion. The non-radiative energy transfer processes also depend on the ion–ion distances, however as R−6. A discussion about the microscopic dopant distributions leading to an efficient single-ion readout quantum computing scheme is here presented. The likely existence of energy transfer paths between the qubits or, as in this case, between the readout ion and the qubit ions, has not been taken into account so far by the rare-earth based quantum computing approaches. The results of this study suggest the need to consider them in order to design realistic and efficient quantum computing schemes for rare-earth doped solids.
We investigate optical emission and absorption in Ce,Pr and Ce,Eu codoped Y2SiO5.We calculate energy transfer microparameters and critical energy transfer distances.We discuss the impact of the energy transfers for rare-earth based quantum computing.We establish limiting distances for an efficient single-ion readout mechanism.
Cavity-assisted quantum memory storage has been proposed for creating efficient (close to unity) quantum memories using weakly absorbing materials. Using this approach, we experimentally demonstrate ...a significant (∼20-fold) enhancement in quantum memory efficiency compared to the no cavity case. A strong dispersion originating from absorption engineering inside the cavity was observed, which directly affects the cavity line width. A more than three orders of magnitude reduction of cavity mode spacing and cavity line width from GHz to MHz was observed. We are not aware of any previous observation of several orders of magnitude cavity mode spacing and cavity line width reduction due to slow light effects.
Many applications of quantum communication crucially depend on reversible transfer of quantum states between light and matter. Motivated by rapid recent developments in theory and experiment, we ...review research related to quantum memory based on a photon‐echo approach in solid state material with emphasis on use in a quantum repeater. After introducing quantum communication, the quantum repeater concept, and properties of a quantum memory required to be useful in a quantum repeater, we describe the historical development from spin echoes, discovered in 1950, to photon‐echo quantum memory. We present a simple theoretical description of the ideal protocol, and comment on the impact of a non‐ideal realization on its quantum nature. We extensively discuss rare‐earth‐ion doped crystals and glasses as material candidates, elaborate on traditional photon‐echo experiments as a test‐bed for quantum state storage, and describe the current state‐of‐the‐art of photon‐echo quantum memory. Finally, we give a brief outlook on current research.
Many applications of quantum communication crucially depend on reversible transfer of quantum states between light and matter. Motivated by rapid recent developments in theory and experiment, this article reviews research related to quantum memory based on a photon‐echo approach in solid state material with emphasis on use in a quantum repeater. After introducing quantum communication, the quantum repeater concept, and properties of a quantum memory required to be useful in a quantum repeater, the historical development from spin echoes, discovered in 1950, to photon‐echo quantum memory is described. Rare‐earth‐ion doped crystals and glasses are discussed as material candidates as well as traditional photon‐echo experiments as a test‐bed for quantum state storage.
Green, blue, violet and ultraviolet upconversion luminescence is reported at room temperature in a YAG: 10.5% Er3+ crystal pumped by one-colour (647 nm) and two-colour (647 + 618 nm) laser ...excitation. The upconversion mechanism was studied by means of time-resolved luminescence spectroscopy and the energy flow pathways are described. Based on the results it appears that energy transfer upconversion is the dominant contribution to the upconverted luminescence upon 647 nm excitation, and excited state absorption is the dominating mechanism upon 647 + 618 nm excitation.
The purely electronic linewidth
δ of terrylene impurity molecules in monocrystalline biphenyl is studied at temperatures
T between 1.7 and 3.5
K using the technique of single-molecule spectroscopy ...(SMS). Based on the data obtained, individual molecules appear to have their own law of
δ(T) dependence; further, hysteresis effects have been observed in thermocycling experiments. The single-molecule (SM) lines investigated quickly broaden and vanish at temperatures between 3 and 3.5
K and reappear after the sample is cooled down again. At
T≈2
K, a slow process of spectral diffusion (SD) was observed on timescales longer than 10
s. To learn about the role of faster SD processes, the technique of intensity–time–frequency correlation (ITFC) SMS was applied to a stable SM line after it had been broadened by 75% as a result of a thermocycling experiment. At 2 and 2.3
K, no significant line broadening could be revealed on timescales between 0.16
ms and 10
s.
We propose a method for efficient storage and recall of arbitrary nonstationary light fields, such as, for instance, single photon time-bin qubits or intense fields, in optically dense atomic ...ensembles. Our approach to quantum memory is based on controlled, reversible, inhomogeneous broadening and relies on a hidden time-reversal symmetry of the optical Bloch equations describing the propagation of the light field. We briefly discuss experimental realizations of our proposal.
Abstract
Objective
The goal of this study was to reach consensus about the best exercise prescription parameters, the most relevant considerations, and other recommendations that could be useful for ...prescribing exercise to patients with migraine.
Methods
This was an international study conducted between April 9, 2022 and June 30, 2022. An expert panel of health care and exercise professionals was assembled, and a 3-round Delphi survey was performed. Consensus was reached for each item if an Aiken V Validity Index ≥ 0.7 was obtained.
Results
The study included 14 experts who reached consensus on 42 items by the third round. The most approved prescription parameters were 30 to 60 minutes of exercise per session, 3 days per week of moderate-intensity continuous aerobic exercise, and relaxation and breathing exercises for 5 to 20 minutes every day. When considering an exercise prescription, initial exercise supervision should progress to patient self-regulation; catastrophizing, fear-avoidance beliefs, headache-related disability, anxiety, depression, physical activity baseline level, and self-efficacy could influence the patients’ exercise participation and efficacy; and gradual exposure to exercise could help improve these psychological variables and increase exercise efficacy. Yoga and concurrent exercise were also included as recommended interventions.
Conclusion
From the experts in the study, exercise prescriptions should be adapted to patients with migraine considering different exercise modalities, such as moderate-intensity aerobic exercise, relaxation, yoga, and concurrent exercise, based on the patients’ preferences and psychological considerations, level of physical activity, and possible adverse effects.
Impact
The consensus reached by the experts can help prescribe exercise accurately to patients with migraine. Offering various exercise modalities can improve exercise participation in this population. The evaluation of the patients’ psychological and physical status can also facilitate the adaptation of the exercise prescription to their abilities and diminish the risk of adverse events.
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