Generation, Manipulation, and Detection of Complex States of Microwave Radiation
OPEN ACCESS
Loading...
Author / Producer
Date
2021
Publication Type
Doctoral Thesis
ETH Bibliography
yes
Citations
Altmetric
OPEN ACCESS
Data
Rights / License
Abstract
Superconducting circuits represent a platform actively researched for its potential use
in quantum information processing. The large couplings achieved between artificial
atoms build out of lossless Josephson junctions and microwave photons are one of the
most prominent features, directly implementing in a circuit the toy models of quantum
electrodynamics (QED). The strong light-matter interaction enables the preparation of
microwave radiation fields in non-classical states, such as states in the single photon
manifold with anti-bunched statistics, that can serve as carriers of quantum bits (qubits)
of information in the prospect of building a network of quantum computing nodes.
The radiation emitted from the superconducting devices can be fully characterized
tomographically by linear amplification and homodyne detection, yielding on average
access to the complete density matrix. However, due to the low energy of microwave
fields, the single-shot detection of individual itinerant photons remained elusive.
In this thesis, I report on a controlled phase gate between a single itinerant photon
and a transmon qubit, which enables a clicking single-shot detector for the photon. We
have characterized the detector’s operation with a quantum source deterministically
emitting superposition of the vacuum and single photon Fock states, and demonstrated
that it performs a quantum non-demolition measurement in the Z-basis. We have
then extended the capabilities of our setup by implementing a parity detector, that
measures whether the number of photons reflected off of it is even or odd, without
providing information on the exact number. This parity detector has allowed us to
access directly the Wigner function of itinerant states of radiation. The strong projective
measurement on a parity eigenspace alters the properties of the measured field,
which we have demonstrated explicitly by heralding Schrödinger cat states, hallmarks
of quantum superposition, from classical coherent states. Finally, I emphasize the capabilities of itinerant fields to act as photonic qubits by describing a novel versatile
source of entangled states of microwave radiation modes. We have realized a unique
superconducting device capable of generating a variety of states within the matrix
product state family, with on the order of ten entangled modes. Their characterization,
via full quantum tomography up to four modes and process maps for larger states, is extensively discussed and expands on the capabilities of the community.
In conclusion, our results demonstrate the generation, manipulation and detection
of complex states of microwave photonic qubits, essential steps to perform distributed
quantum information processing with the superconducting circuit architecture. In
particular, the demonstrated technology puts a universal quantum gate set for itinerant
microwave photons, and super-sensitive photon measurements such as Heisenberg-limited phase metrology, within immediate reach.
Permanent link
Publication status
published
External links
Editor
Contributors
Examiner : Wallraff, Andreas
Examiner : Imamoglu, Atac
Examiner : Nakamura, Yasunobu
Book title
Journal / series
Volume
Pages / Article No.
Publisher
ETH Zurich
Event
Edition / version
Methods
Software
Geographic location
Date collected
Date created
Subject
Organisational unit
03720 - Wallraff, Andreas / Wallraff, Andreas