Advances in Atomic, Molecular, and Optical Physics (eBook)

Benjamin Bederson, Herbert Walther (Herausgeber)

eBook Download: PDF

2001 | 1. Auflage
300 Seiten
Elsevier Science (Verlag)
978-0-08-052606-5 (ISBN)

Infos

This series, established in 1965, is concerned with recent developments in the general area of atomic, molecular, and optical physics. The field is in a state of rapid growth, as new experimental and theoretical techniques are used on many old and new problems. Topics covered also include related applied areas, such as atmospheric science, astrophysics, surface physics, and laser physics. Articles are written by distinguished experts who are active in their research fields. The articles contain both relevant review material and detailed descriptions of important recent developments.

Inhalt

Front Cover 1
Advances in Atomic, Molecular, and Optical Physics 4
Copyright Page 5
Contents 6
Contributors 8
Chapter 1. Femtosecond Quantum Control 12
I. Introduction 12
II. Experimental Techniques 17
III. One-Parameter Quantum Control in the Gas Phase 23
IV. Adaptive Femtosecond Pulse Shaping 34
V. Many-Parameter Quantum Control in the Gas Phase 40
VI. Many-Parameter Quantum Control in the Liquid Phase 51
VII. Summary and Outlook 57
VIII. Acknowledgments 59
IX. References 59
Chapter 2. Coherent Manipulation of Atoms and Molecules by Sequential Laser Pulses 66
I. Introduction 68
II. Principles of Coherent Excitation 78
III. Three-State STIRAP: Theory 93
IV. Three-State STIRAP: Experiments 114
V. STIRAP-Like Population Transfer in Multistate Chains 128
VI. Adiabatic Momentum Transfer 137
VII. Branched-Chain Excitation 146
VIII. Population Transfer via a Continuum of Intermediate States 154
IX. Extensions and Applications of STIRAP 167
X. Propagation Phenomena 173
XI. Applications of STIRAP in Quantum Optics and Quantum Information 184
XII. Summary and Outlook 190
XIII. Acknowledgments 191
XIV. References 191
Chapter 3. Slow, Ultraslow, Stored, and Frozen Light 202
I. Introduction 202
II. Group Velocity: Kinematics 204
III. Slow Light 207
IV. Ultraslow Light 220
V. Storing and Retrieving Quantum Information 225
VI. The Ultimate Slow Light: Frozen Light 230
VII. Applications 236
VIII. Conclusion 247
IX. References 248
Chapter 4. Longitudinal Interferometry with Atomic Beams 254
I. Introduction 254
II. Interference in Ion–Atom Collisions 256
III. Differentially Detuned Separated Oscillatory Fields: DSOF 263
IV. Amplitude Modulation and Rephasing 266
V. Detecting Longitudinal Momentum Coherences 269
VI. Discussion of the Semiclassical Approximation 270
VII. Apparatus and Experimental Techniques 271
VIII. Density Matrix Deconvolution 274
IX. Search for Longitudinal Coherences in an Unmodified Atomic Beam 279
X. Conclusion 283
XI. Acknowledgments 284
XII. References 284
Subject Index 288
Contents of Volumes in This Series 300
Errata 312

Textauszug

Coherent Manipulation of Atoms Molecules By Sequential Laser Pulses

N.V. Vitanov*    Helsinki Institute of Physics, PL 9, 00014 University of Helsinki, Finland

M. Fleischhauer    Fachbereich Physik, Universität Kaiserslautern, 67653 Kaiserslautern, Germany

B.W. Shore1    Lawrence Livermore National Laboratory, Livermore, California 94550

K. Bergmann    Fachbereich Physik, Universität Kaiserslautern, 67653 Kaiserslautern, Germany
* N. V. Vitanov is also affiliated with the Department of Physics, Sofia University, James Boucher 5 blvd., 1126 Sofia, Bulgaria, and Institute of Solid State Physics, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria.
1 Retired

I Introduction

Many branches of contemporary physics require atoms or molecules prepared in specified quantum states—not only for traditional studies of state-to-state collision dynamics, isotope separation, or laser-controlled chemical reactions, but also in more recently developing research areas of atom optics and quantum information. Of greatest interest is the fraction of all atoms or molecules in a specific state, a time-varying probability here termed the population P(t). Schemes for transferring population selectively (i.e., to a single predetermined quantum state), such as excitation with frequency-swept pulses and stimulated Raman adiabatic passage (STIRAP), have opened new opportunities for coherent control of atomic and molecular processes. With the growing interest in quantum information, there is also concern with creating and controlling specified coherent superpositions of quantum states. These more general properties of an ensemble of atoms or molecules are embodied in the time-varying state vector Ψ(t).

This chapter describes the basic principles underlying a variety of techniques that can be used to control state vectors and, in particular, to transfer population, selectively, between quantum states of atoms or molecules. We also describe experimental demonstrations of the various principles. (Aspects of these population transfer schemes have been reviewed by Vitanov et al., 2001.) All the methods share a common reliance on adiabatic time evolution, induced by a sequence of delayed, but partially overlapping, laser pulses. They begin with an ensemble of atoms or molecules in which the population is in a specified discrete quantum state. Then the sequence of laser pulses forces the population into a desired target state. Only highly monochromatized light can provide the selectivity needed to isolate a single final state—broadband light or charged particle pulses cannot so discriminate. The control of phase imposes further constraints; it requires coherent radiation, available only from a laser.

One goal of the theory of coherent excitation is to predict, for a given set of radiation pulses, the probability that atoms will undergo a transition between the initial state and the desired target state (the population transfer efficiency). More generally, theory can predict the changes of a state vector Ψ(t) produced by specified radiation. Alternatively, theory can provide a prescription for pulses that will produce a desired population transfer or state vector change.

We begin our discussion, in Section I.A, with a brief summary of the historical background for the subsequent discussions of adiabatic transfer schemes. Although the excitation techniques described in this chapter require coherent radiation, incoherent light, such as that from filtered atomic vapor lamps or from broadband lasers with poor coherence properties, also has very useful applications for selective excitation, some of which are described briefly in Section I.B. Coherent excitation differs qualitatively from incoherent excitation. To emphasize this difference, Section I.C contrasts some simple examples.

Starting with Section II, we develop the general mathematical principles needed to describe coherent excitation and adiabatic time evolution of quantum systems. In Section III we apply this to the basic STIRAP process, wherein adiabatic evolution produces complete population transfer in a three-state Raman system. Section IV discusses various experimental demonstrations of the STIRAP technique. Sections V–VIII describe various theoretical and experimental extensions of the original three-state STIRAP. Although our primary concern is with the effect of prescribed fields on atoms, the atomic excitation creates localized polarization which alters the radiation as it propagates; Section X discusses some of the effects to be found by treating the field and the atoms together. Section XI discusses some applications of the STIRAP principles in the rapidly growing area of quantum information and in the general area of quantum optics. Section XII offers a summary and comments on possible future work.

A EARLY DAYS OF LASER STATE SELECTION

The use of lasers to address individual states in atoms or molecules dates back more than 30 years [for reviews see Bergmann (1988), Rubahn and Bergmann (1990)]. The early work, taking advantage of the small bandwidth and high spectral power density of laser radiation, employed lasers to populate individual rotational-vibrational levels in an electronically excited state of molecules, as preparation for collision studies (Kurzel and Steinfeld 1970; Bergmann and Demtröder, 1971) or for spectroscopic analysis (Demtröder et al., 1969). Later, individual thermally populated states in the electronic ground state were labeled through population depletion by optical pumping (Bergmann et al., 1978; Gottwald et al., 1986). That work paved the way for detailed studies in crossed molecular beams involving molecules in preselected rotational (Hefter et al., 1981) or individual vibrational states (Ziegler et al., 1988) colliding with atoms (Gottwald et al., 1987) or electrons (Ziegler et al., 1987). By 1986 laser state selection by population depletion had even been developed sufficiently to allow collision studies of molecules in individual magnetic sublevels (Mattheus et al., 1986; Hefter et al., 1986) with high resolution of the scattering angle.

State selection by population depletion through optical pumping is limited to thermally populated levels. Access to higher lying vibrationally excited levels in the electronic ground state was gained by the Franck–Condon pumping method (Rubahn and Bergmann, 1990) whereby excitation, from thermally populated levels (j′, v′), into a suitably chosen rovibrational level (j″, v″) in the electronically excited state, followed by spontaneous decay back to the electronic ground state, establishes a distribution fv′ (v″) of population over vibrationally excited levels v″. Within the limits given by the optical transition rates, the distribution fv′(v″) can be controlled by a suitable choice of the level v′.

In the early 1980s, high-power pulsed lasers became more readily available and a variety of other schemes for laser state selection, in particular for the population of vibrationally excited levels in the electronic ground state, such as overtone pumping (OTP) (Crim, 1984) or off-resonance stimulated Raman scattering (ORSRS) (Orr et al., 1984; Meier et al., 1986), were developed. In OTP, levels v″ > 1 are directly excited from v″ = 0 in a single photon transition. High laser power is needed because the transition probability decreases rapidly with Δv″. Only a small fraction of the molecules are typically excited to high-lying levels. In ORSRS the frequency difference between a strong (possibly fixed frequency) laser and a tunable laser matches the transition frequency between rotational levels in the vibrational states v″ = 0 and v″ = 1. A substantial fraction (< 50%) of the molecules in a given state (j″, v″ = 0) can be excited to v″ = 1.

Another two-step process, stimulated emission pumping (SEP) (Kittrell et al., 1981), has proven to be a flexible and very successful method for population transfer. In SEP a suitable level in an electronic state is excited. Rather than allowing spontaneous emission to distribute the population over many vibrational levels, another laser, the frequency of which is tuned to resonance with the desired target state, forces as much as 50% of the electronically exited molecules into that state. However, about 50% of the population will remain in the excited electronic state and will subsequently be distributed by spontaneous emission over other vibrational levels v″.

In the context of this early work the coherence properties of the radiation were not essential. It was therefore natural, in seeking to improve the flexibility of state selection, to look for schemes...

Produkt-Details

• Erscheint lt. Verlag: 26.9.2001
• Sprache: englisch
• Themenwelt: Sachbuch/Ratgeber
• Themenwelt: Naturwissenschaften ► Physik / Astronomie ► Atom- / Kern- / Molekularphysik
• Themenwelt: Naturwissenschaften ► Physik / Astronomie ► Hochenergiephysik / Teilchenphysik
• Themenwelt: Naturwissenschaften ► Physik / Astronomie ► Optik
• Themenwelt: Technik
• ISBN-10: 0-08-052606-3 / 0080526063
• ISBN-13: 978-0-08-052606-5 / 9780080526065