共查询到20条相似文献,搜索用时 156 毫秒
1.
We demonstrate a controlled phase change of π in a degenerate superposition by altering a laser frequency by only 10 MHz. The method relies on the preparation of an adiabatic state involving the M = ±2 and M = 0 states of the 3P2 (J = 2) level of metastable neon. Dependent on the frequency, the preparation proceeds either by stimulated Raman adiabatic passage (STIRAP) or by coherent population trapping (CPT). In the former case the superposition is prepared by adiabatic transfer induced in an extended tripod linkage scheme. In the latter case population is optically pumped into the Zeeman manifold of the level 3P2. The population which does not reach a dark state decays to the ground state of neon. The amplitudes and relative phases of the dark states differ for the two cases. The phase change is monitored using the method of phase-to-population mapping. 相似文献
2.
Stimulated Raman adiabatic passage (STIRAP) is a well established technique whereby two pulses, S preceding P, induce complete population transfer between states 1 and 3 of a three-state chain, 1-2-3. Traditionally, the S and P pulse envelopes are taken as positive (often with Gaussian form of time dependence). However, when the envelope undergoes a sign change during the pulse, as occurs with pulses in which an abrupt phase change of π occurs and whose temporal area (time-integrated Rabi frequency) is zero, then the simple population transfer need not occur. Instead there may occur multiple adiabatic passages, in which the population may ultimately be left in either state 1 (a double STIRAP) or state 3 (a triple STIRAP) or, with suitable pulse delay, in a superposition of these two states. These adiabatic changes offer possibilities to produce final-state probability amplitudes with either positive or negative signs. We here show simulated examples of such behavior, and discuss the adiabatic conditions needed for such excitation to occur. 相似文献
3.
M. Amniat-Talab M. Saadati-Niari S. Guérin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2012,66(8):1-9
We propose two relatively robust schemes to generate entangled W states of three (or generally N) ions in ion trap systems by using adiabatic passage technique and appropriately designed ion-field couplings in a single step. In the first scheme, we apply the N-pod fractional stimulated Raman adiabatic passage (F-STIRAP) technique to generate W state of N ions using two Gaussian laser pulses. We also show that the W state of N ? 1 ions can be created via a simple N-pod standard STIRAP by two laser pulses. In the second scheme, we generate the entangled state of N ions via ??-pulse technique by a single laser pulse. We also study the population transfer of the system by numerical solutions of the master equation, considering the effect of decoherence channels due to laser intensity fluctuations and dissipation in the phonon modes. 相似文献
4.
A theoretical analysis is presented of the effect of correlation between fluctuations of laser pulse amplitudes on population
transfer between the states of a three-level atom coupled by the laser field. The carrier frequencies of the pulses are tuned
to resonance with the transitions between the ground and excited states, |〈 and | 2〈, and the excited and metastable states,
|2〈 and |3〈, in a lambda-type configuration. The laser pulses are timed so that population transfer between states |1〈 and
| 3〈 is made possible by stimulated Raman adiabatic passage (STIRAP) in the absence of fluctuations. STIRAP does not occur
when the laser fields are not correlated. When the fluctuations of one pulse amplitude duplicate those of the other, STIRAP
can be observed for pulse amplitudes larger than those required in the absence of fluctuations. 相似文献
5.
Jun He Yong-Sheng Zhang Xiang-Fa Zhou Qun-Feng Chen Guang-Can Guo 《Optics Communications》2009,282(6):1167-1170
An method for adiabatic population transfer and the preparation of an arbitrary quantum superposition state using the oscillating dark states (ODS) in atomic system is presented. Quantum state of a three-level Λ configuration atomic system finally evolves into the same time-dependent state, and oscillates periodically between two ground levels under evolving adiabatic conditions when two pairs of classical detuning laser fields drive the system into the ODS forcedly, whatever the initial states of the system are. The decoherence of the ODS evolution is greatly suppressed and the oscillation is very stable, therefore adiabatic population transfer and the preparation of an arbitrary quantum superposition state of atomic system can be completed accurately and conveniently. 相似文献
6.
N.V. Vitanov B.W. Shore K. Bergmann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(1):15-29
The well-known process of stimulated Raman adiabatic passage (STIRAP) provides a robust technique for achieving complete population
transfer between the first and last state of a three-state chain, with little population, even transiently, in the intermediate
state. The extension of STIRAP to general N-state chainwise-linked systems continues to generate interest. Recently Malinovsky and Tannor (Phys. Rev. A 56, 4929 (1997)) have shown with numerical simulation that a resonant pulse sequence, which they term “straddle STIRAP”, can
produce (under appropriate conditions, including specific pulse areas) complete population transfer with very little population
in intermediate states. Their proposal supplements a pair of counterintuitively ordered delayed laser pulses, driving the
first and last transition of the chain and corresponding to the pump and Stokes pulses in STIRAP, with one or more additional
strong pulses of longer duration which couple the intermediate transition(s) and overlap both the pump and the Stokes pulses.
In this paper, we modify the “straddling” Malinovsky-Tannor pulse sequence so that the intermediate couplings are constant (and strong), at least during the times when the pump and Stokes pulses are present, and the intermediate states therefore
act as a strongly coupled subsystem with constant eigenvalues. Under this condition, we show that the original N-state chain is mathematically equivalent to a system comprising N-2 parallel -transitions, in which the initial state is coupled simultaneously to N-2 dressed intermediate states, which in turn are coupled to the final state. The population transfer is optimized by suitably
tuning the pump and Stokes frequencies to resonance with one of these dressed intermediate states, which effectively acts
as the single intermediate state in a three-state STIRAP-like process. We show that tuning to a dressed intermediate state
turns the system (for both odd N and even N) into a three-state system - with all of the properties of conventional STIRAP (complete population transfer, little transient
population in the intermediate states, insensitivity to variations in the laser parameters, such as pulse area). The success
of the tuning-to-dressed-state idea is explained by using simple analytic approaches and illustrated with numerical simulations
for four-, five-, six- and seven-state systems.
Received: 17 April 1998 / Accepted: 15 June 1998 相似文献
7.
R. Unanyan S. Guérin B. W. Shore K. Bergmann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(3):443-449
In traditional schemes of multilevel multilaser excitation, each laser pulse interacts with only one pair of states, and the
rotating wave approximation (RWA) is applicable. Here we study the population transfer process in a three-state system when
each of the two lasers interacts with each of the pair of states and when the Rabi frequencies characterizing the interaction
strengths of the system are comparable to or larger than the difference of the transition frequencies. We show that complete
and robust population transfer is possible under conditions more general than those hitherto considered necessary for stimulated
Raman adiabatic passage (STIRAP) or for successive π pulses. Using adiabatic Floquet theory we show that successful population transfer can be interpreted as adiabatic passage
by means of a transfer state which connects the initial and final states. The Floquet picture offers a convenient interpretation
of the population transfer as accompanied by multiple absorption of photons from or emission into the laser fields. 相似文献
8.
Creation of coherent superpositions in quantum systems with Na states in the lower set and Nb states in the upper set is presented. The solution is drived by using the Morris–Shore transformation, which step by step reduces the fully coupled system to a three-state Λ-like system and a set of decoupled states. It is shown that, for properly timed pulse, robust population transfer from an initial ground state (or superposition of M ground states) to an arbitrary coherent superposition of the ground states can be achieved by coincident pulses and/or STIRAP techniques. 相似文献
9.
We propose schemes to prepare atomic entangled states in a bi-mode cavity via stimulated Raman adiabatic passage (STIRAP) and fractional stimulated Raman adiabatic passage (f-STIRAP) techniques. Our scheme should be realizable in the near future because of the existence of all experimental ingredients. Our numerical simulation shows we can entangle the atoms with high fidelities by choosing proper laser pulses. 相似文献
10.
We experimentally demonstrate coherent population transfer, driven by stimulated Raman adiabatic passage (STIRAP) between two bound quantum states, coupled via a continuum of states. We present extended numerical and experimental investigations on population transfer from the metastable state 2s 1S0 to the excited state 4s 1S0 in metastable helium atoms. While techniques based on incoherent excitation do not permit any population transfer via rapidly decaying continuum states, our data indicate a maximum transfer efficiency of 20% in coherent excitation by STIRAP. We study the transfer efficiency with respect to the relevant experimental parameters. 相似文献
11.
从原子-二聚物分子转化系统的非U(1)对称性出发,将保真度的定义推广到了非线性系统.并利用绝热保真度定量地研究了原子-二聚物分子转化系统在受激拉曼绝热过程中的动力学和绝热性.研究发现,这个系统的相干布居俘获态——暗态的绝热保真度作为绝热参量的函数以幂律关系趋于1.这个函数关系与线性系统的绝热参量和绝热保真度的幂律关系非常相似,但该系统的幂指数要远小于线性系统的幂指数.此外,还进一步讨论了如何通过优化受激拉曼绝热过程的外部参量得到更高的绝热保真度,从而优化系统的绝热性,提高原子-分子转化效率.
关键词:
原子-二聚物分子转化系统
暗态
受激拉曼绝热过程
绝热保真度 相似文献
12.
Vewinger F Heinz M Garcia Fernandez R Vitanov NV Bergmann K 《Physical review letters》2003,91(21):213001
We demonstrate experimental techniques for creating and measuring a coherent superposition of two degenerate atomic states with equal amplitudes in metastable neon. Starting from state (3)P(0), we create adiabatically a coherent superposition of the magnetic sublevels M=+/-1 of the state (3)P(2) using a tripod stimulated Raman adiabatic passage scheme. The measurement is based on the coupling of the levels (3)P(2)<-->(3)P(1) by a linearly polarized laser, followed by the detection of the population in the (3)P(2)(M=+/-2) states as a function of the polarization angle of that laser. 相似文献
13.
We show that a robust macroscopic atom-molecule dark state can exist in fermionic systems, which represents a coherent superposition between the ground molecular Bose-Einstein condensates and the atomic BCS paired state. We take advantage of the tunability offered by external laser fields, and explore this superposition for demonstrating coherent oscillations between ground molecules and atom pairs. We interpret the oscillation frequencies in terms of the collective excitations of the dark state. 相似文献
14.
M. J. Mark J. G. Danzl E. Haller M. Gustavsson N. Bouloufa O. Dulieu H. Salami T. Bergeman H. Ritsch R. Hart H.-C. N?gerl 《Applied physics. B, Lasers and optics》2009,95(2):219-225
One possible way to produce ultra-cold, high-phase-space-density quantum gases of molecules in the rovibronic ground state
is given by molecule association from quantum-degenerate atomic gases on a Feshbach resonance and subsequent coherent optical
multi-photon transfer into the rovibronic ground state. In ultra-cold samples of Cs2 molecules, we observe two-photon dark resonances that connect the intermediate rovibrational level |v=73,J=2〉 with the rovibrational ground state |v=0,J=0〉 of the singlet X
1
Σ
g
+ ground-state potential. For precise dark resonance spectroscopy we exploit the fact that it is possible to efficiently populate
the level |v=73,J=2〉 by two-photon transfer from the dissociation threshold with the stimulated Raman adiabatic passage (STIRAP) technique.
We find that at least one of the two-photon resonances is sufficiently strong to allow future implementation of coherent STIRAP
transfer of a molecular quantum gas to the rovibrational ground state |v=0,J=0〉. 相似文献
15.
Sergey A. Podoshvedov 《Optics Communications》2012,285(18):3896-3905
We propose an approach with displaced states to use it for rotations of base coherent states and squeezed coherent states. Our approach is based on representation of the coherent states in free-traveling fields in terms of displaced number states with arbitrary amplitude of displacement. Two optical schemes are developed for construction of Hadamard gate for the base states. One of the optical schemes is based on alternation of photon additions and displacement operators (in general case, N-photon additions and N?1-displacements are required) to generate displaced squeezed even/odd superposition of coherent states (SCSs) with high fidelity in dependency on type (computational zero or one) of the base input state. Another optical scheme uses two-photon subtracted squeezed coherent states to approximate outcome of the Hadamard gate for the base squeezed coherent states. Output states approximate with high fidelity either even squeezed SCS or odd SCS shifted relative to each other by some value. It enables to adjust the optical scheme for construction of the Hadamard gate being mainframe element for quantum computation with basic squeezed coherent states. 相似文献
16.
17.
本文讨论了在双Λ型原子系统中制备相干叠加态的方法:一个Λ型系统通过控制激光而另一个Λ型系统采用部分受激拉曼绝热通道的方法.在理论上分析了产生任意相干叠加态的可能性并且讨论了透热系统在产生相干叠加态过程中的重要性.研究表明,没有透热过程是不可能制备出任意的叠加态.应用数值方法验证理论分析是正确,并且指出任意叠加态的产生只与控制脉冲的时间延迟有关. 相似文献
18.
19.
We demonstrate significant enhancement of four-wave mixing in coherently driven mercury isotopes to generate vacuum-ultraviolet radiation at 125 nm. The enhancement is accomplished by preparation of the mercury atoms in a state of maximum coherence, i.e. maximum nonlinear-optical polarization, driven by Stark-chirped rapid adiabatic passage (SCRAP). In this technique, a pump laser at 313 nm excites the two-photon transition between the ground state 6s21S0 and the target state 7s 1S0 in mercury. A strong, off-resonant radiation field at 1064 nm generates dynamic Stark shifts. These Stark shifts serve to induce a rapid adiabatic passage process on the two-photon transition. During the process a coherent superposition of the two states is established, which enhances the nonlinear-optical polarization in the medium to the maximum possible value. The maximum coherence permits efficient four-wave mixing of a pump laser and an additional probe laser at 626 nm. The efficiency is further enhanced, as the SCRAP process allows to stimulate the complete set of different mercury isotopes to participate in the frequency conversion process. This enlarges the effective atomic density of the medium. Thus, we observe the generation of vacuum-ultraviolet radiation at 125 nm enhanced by more than one order of magnitude with respect to conventional frequency conversion. Parallel to the frequency conversion process, we monitored the evolution of the population in the medium by laser-induced fluorescence. These data demonstrate efficient coherent population transfer by SCRAP. 相似文献
20.
An analogy is explored between a setup of three atomic traps coupled via tunneling and an internal atomic three-level system interacting with two laser fields. Within this scenario we describe a STIRAP like process which allows to move an atom between the ground states of two trapping potentials and analyze its robustness. This analogy is extended to other robust and coherent transport schemes and to systems of more than a single atom. Finally it is applied to manipulate external degrees of freedom of atomic wave packets propagating in waveguides. 相似文献