Chapter 3
Quantum Optical Phenomena in Nuclear
Resonant Scattering
Ralf Röhlsberger and Jörg Evers
Abstract With the advent of high-brilliance, accelerator-driven light sources such
as modern synchrotron radiation sources or x-ray lasers, it has become possible
to extend quantum optical concepts into the x-ray regime. Owing to the availability of single photon x-ray detectors with quantum efficiencies close to unity and
photon-number resolving capabilities, fundamental phenomena of quantum optics
can now also be studied at Angstrom wavelengths. A key role in the emerging field
of x-ray quantum optics is taken by the nuclear resonances of Mössbauer isotopes.
Their narrow resonance bandwidth facilitates high-precision studies of fundamental
aspects of the light-matter interaction. A very accurate tuning of this interaction is
possible via a controlled placement of Mössbauer nuclei in planar thin-film waveguides that act as cavities for x-rays. A decisive aspect in contrast to conventional
forward scattering is that the cavity geometry facilitates the excitation of cooperative
radiative eigenstates of the embedded nuclei. The multiple interaction of real and
virtual photons with a nuclear ensemble in a cavity leads to a strong superradiant
enhancement of the resonant emission and a strong radiative level shift, known as collective Lamb shift. Meanwhile, thin-film x-ray cavities and multilayers have evolved
into an enabling technology for nuclear quantum optics. The radiative coupling of
such ensembles in the cavity field can be employed to generate atomic coherences
between different nuclear levels, resulting in phenomena including electromagnetically induced transparency, spontaneously generated coherences, Fano resonances
and others. Enhancing the interaction strength between nuclei in photonic structures
like superlattices and coupled cavities facilitates to reach the regime of collective
R. Röhlsberger (B)
Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
e-mail: ralf.roehlsberger@desy.de
Helmholtz Centre for Heavy Ion Research (GSI), Planckstr. 1, 64291 Darmstadt, Germany
J. Evers
Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
e-mail: joerg.evers@mpi-hd.mpg.de
© Springer Nature Singapore Pte Ltd. 2021
Y. Yoshida and G. Langouche (eds.), Modern Mössbauer Spectroscopy,
Topics in Applied Physics 137, https://doi.org/10.1007/978-981-15-9422-9_3
105
Quantum Optical Phenomena in Nuclear
Resonant Scattering
Ralf Röhlsberger and Jörg Evers
Abstract With the advent of high-brilliance, accelerator-driven light sources such
as modern synchrotron radiation sources or x-ray lasers, it has become possible
to extend quantum optical concepts into the x-ray regime. Owing to the availability of single photon x-ray detectors with quantum efficiencies close to unity and
photon-number resolving capabilities, fundamental phenomena of quantum optics
can now also be studied at Angstrom wavelengths. A key role in the emerging field
of x-ray quantum optics is taken by the nuclear resonances of Mössbauer isotopes.
Their narrow resonance bandwidth facilitates high-precision studies of fundamental
aspects of the light-matter interaction. A very accurate tuning of this interaction is
possible via a controlled placement of Mössbauer nuclei in planar thin-film waveguides that act as cavities for x-rays. A decisive aspect in contrast to conventional
forward scattering is that the cavity geometry facilitates the excitation of cooperative
radiative eigenstates of the embedded nuclei. The multiple interaction of real and
virtual photons with a nuclear ensemble in a cavity leads to a strong superradiant
enhancement of the resonant emission and a strong radiative level shift, known as collective Lamb shift. Meanwhile, thin-film x-ray cavities and multilayers have evolved
into an enabling technology for nuclear quantum optics. The radiative coupling of
such ensembles in the cavity field can be employed to generate atomic coherences
between different nuclear levels, resulting in phenomena including electromagnetically induced transparency, spontaneously generated coherences, Fano resonances
and others. Enhancing the interaction strength between nuclei in photonic structures
like superlattices and coupled cavities facilitates to reach the regime of collective
R. Röhlsberger (B)
Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
e-mail: ralf.roehlsberger@desy.de
Helmholtz Centre for Heavy Ion Research (GSI), Planckstr. 1, 64291 Darmstadt, Germany
J. Evers
Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
e-mail: joerg.evers@mpi-hd.mpg.de
© Springer Nature Singapore Pte Ltd. 2021
Y. Yoshida and G. Langouche (eds.), Modern Mössbauer Spectroscopy,
Topics in Applied Physics 137, https://doi.org/10.1007/978-981-15-9422-9_3
105