http://events.kias.re.kr/h/qm2019/
KIAS 2019 Workshop on
Quantum Metrology
July 29 (Monday) - July 31 (Wednesday), 2019
KIAS, Seoul, Korea [Rm 1503, Bldg 1] Hosted by KIAS and QuIST *** There is no registration fee, |
| Abstracts | Home > Abstracts |
1. YongSiah Teo
Tutorial Talk:
Title: A condensed ABC of quantum tomography
Abstract: I shall give a concise introductory talk on quantum tomography. This includes:
- State tomography: informational completeness, linear inversion (noiseless), maximum
likelihood (noisy);
- Precision study: Fisher information (optimal measurements and measurement
certification), quantum Fisher information (optimal quantum metrology);
- Error analysis: Bayesian error regions.ek.
Research Talk:
Title: Adaptive compressive tomography with no a priori information: recent results
Abstract: If one knows that a given unknown state is at most of rank r, then the standard
technique of compressed sensing (CS) allows for a strictly informationally complete
(strictly-IC) characterization of the state using a specialized rank-r CS measurement with
quantum positivity constraints enforced and few measurement settings. The a priori
knowledge of the value of r however requires experimental verification. In this talk, I shall
propose a novel and practical scheme of adaptive compressed tomography (ACT) (Phys.
Rev. Lett. 122, 100404, 2019) with which the required strictly-IC measurement settings are
adaptively found based on only a posteriori information encoded in the measurement data,
and a clever state-space inspection technique that relies on the properties of convex
optimization. This scheme thus achieves compression without the need for any a priori
information about the unknown state, which includes its rank and proximity to some target
state. Finally, I shall list a few interesting new numerical results and conjectures that can
be found in an upcoming Phys. Rev. A publication very soon.
2. Junho Suh
Title: Nanomechanical resonators for quantum measurements
Abstract: Nanomechanical resonators provide a versatile platform for high-sensitivity sensors.
These tiny devices reached quantum regime recently allowing actuations and
measurements near zero-point motion. Cavity electromechanical systems are one of the
successful examples as demonstrated by quantum back-action evading measurements[1]
and quantum squeezing of mechanical motion[2-3]. In order to exploit these quantum
electromechanical devices for sensing applications, realiable ground state generation and
quantum noise manipulation are necessary. We focus on enhancing photon-phonon
coupling toward this goal, and in this talk, I describe our recent approaches involving gatetunable
nanowire junctions that could overcome the geometric capacitance limit in
nanomechanical cavity electromechanical devices.
[1] Suh et.al., Science 344, 1262-1265 (2014).
[2] Wollman et.al., Science 349, 952-955 (2015).
[3] Lei et.al., PRL 117, 100801 (2016).
3. Ranjith Nair
Quantum state discrimination: Theory & Applications
A tutorial introduction to the theory of quantum state discrimination will be given. A
selection of topics will be covered from among binary & M-ary state discrimination,
unambiguous state discrimination and state separation, and asymptotic state
discrimination. Connections of the theory to other areas of quantum information science
and applications to communications, sensing, and metrology will be highlighted.
Superresolution of incoherent optical sources: Breaking the Rayleigh limit
The Rayleigh limit for resolution of two incoherent point sources has long been regarded
as a benchmark for the resolving power of an optical system. A fresh approach to the
problem through the prism of quantum metrology reveals that this limit is an artifact of
limiting oneself to the traditional approach of direct imaging and that there is no such
fundamental resolution limit imposed by quantum mechanics even when the sources are
arbitrarily close. Further, we show that there are spatial mode-resolving linear optics
measurements that can approach the quantum-limited performance in estimating the
separation of the sources.
4. Changhyoup Lee
Tutorial: Classical optical sensors and the shot-noise limit
Research: Quantum optical sensors and applications
5. Tim Byrnes
Title 1: Remote quantum clock synchronization without synchronized clocks
Abstract: A major outstanding problem for many quantum clock synchronization protocols is the
hidden assumption of the availability of synchronized clocks within the protocol. In general,
quantum operations between two parties do not have consistent phase definitions of quantum
states, which introduce an unknown systematic phase error. We show that despite prior
arguments to the contrary, it is possible to remove this unknown phase via entanglement
purification. This closes the loophole for entanglement based quantum clock synchronization
protocols, which are most compatible with current photon based long-distance entanglement
distribution schemes. Starting with noisy Bell pairs, we show that the scheme produces a singlet
state for any combination of (i) differing basis conventions for Alice and Bob; (ii) an overall time
offset in the execution of the purification algorithm; and (iii) the presence of a noisy channel. Error
estimates reveal that better performance than existing classical Einstein synchronization protocols
should be achievable using current technology.
Title 2: Adiabatic Quantum Computation with qubit ensembles
Abstract: Traditionally quantum computing approaches have been formulated in terms of either discrete (qubit) or continuous variables. Our approach offers an alternative third path, naturally suited towards implementations in cold atom ensembles and BECs. In the standard approach to adiabatic quantum computing (AQC), quantum information stored on qubits are adiabatically evolved to find the lowestenergy state of a problem Hamiltonian. Here we investigate a variation of AQC where spin ensembles are used in place of qubits. The use of ensembles duplicates the quantum information, and allows errors to be suppressed during the adiabatic evolution. For large ensemble sizes, we find that the minimum gap for large ensembles is well predicted by mean-field theory and the AQC performance can be shown to improve with ensemble size, realizing error-suppression. While there are problem instances where the minimal gap can decrease, the number of these instances is suppressed for large ensemble sizes. Our approach shows that it is possible to perform AQC without the necessity of controlling individual qubits, which allows for an alternative route towards implementing AQC.
6. Sun Kyung Lee
Title: Frequency comb single-photon interferometry via induced coherence
Abstract : We demonstrate a frequency comb single-photon interferometry for quantum
spectroscopy and imaging with undetected photons by utilizing both of optical frequency
comb technique and quantum erasing mechanism with path-entangled photon pairs
generated from dual parametric down-conversions. By letting the induced one photon
interference of signal beam is modulated by transmission coefficient of the optical sample
located in an idler path, it enables us to engineer a quantum state of frequency encoded
photons remotely with differently colored conjugate photons as well as to measure optical
property of the material with undetected photons.
7. Su-Yong Lee
Tutorial: Quantum states in quantum-enhanced metrology.
Research: Entangled states in lossy quantum-enhanced metrology
8. Changhun Oh
Title: Toward optimal Gaussian metrology
9. Young-Sik Ra
Title: Multimode quantum states of light based on optical frequency comb
Abstract: I will present generation of multimode quantum states of light in the continuous-variable domain. To generate multimode quantum states, we exploit the multimode nature of optical frequency comb: optical frequency comb is used as a pump laser for the parametric down-conversion process, which results in multimode squeezed vacuum states. Furthermore, the generated states, which are Gaussian quantum states, are converted into non-Gaussian quantum states by subtracting a single photon from a chosen mode. Such multimode quantum states will play essential roles for quantum metrology, especially for multiple parameter estimation.
10. Changsuk Noh
Title: Output squeezing in quantum Rabi model
Abstract: Squeezing is an important source in quantum metrology. In this talk, I will discuss squeezing properties of the output field for a weakly-driven dissipative quantum Rabi model. For the atom-field coupling strength ranging from the conventional strong-coupling regime to the deep-strong coupling regime, I will discuss how we can calculate the squeezing spectrum of the output field using a combination of a master equation and input-output theory. After optimization over the system-bath coupling strength and the driving field strength, the overall squeezing is shown to increase with the interaction strength.