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QFarm

QFarm Quantum Seminar Series

Q-FARM presents "Coupling diamond defects to high-finesse optical microcavities"

Topic: 
Coupling diamond defects to high-finesse optical microcavities
Abstract / Description: 

Defect centers in diamond can offer atomic-like optical transitions and long-lived spin degrees of freedom. Integrating them into high quality optical resonators opens a route toward realizing a cavity quantum electrodynamics system combining atomic-like coherence with a robust solid-state platform. While approaches based on diamond nanophotonics have been pursued for more than a decade, Fabry-Perot microcavities present a complementary approach that has recently received significant attention. This talk will consider the potential benefits and challenges to open micro-cavities, and examine progress toward coupling them to diamond defect centers

Date and Time: 
Wednesday, February 24, 2021 - 12:00pm

Q-FARM presents "Direct laser cooling of polyatomic molecules"

Topic: 
Direct laser cooling of polyatomic molecules
Abstract / Description: 

Laser cooling and evaporative cooling are the workhorse techniques that have revolutionized the control of atomic systems. In recent years, direct laser cooling has been successfully adapted to several diatomic molecules and now we seek to broaden these successes by extending its use to polyatomic molecules. The complex vibrational and rotational structure of polyatomic molecules makes it challenging to photon cycle but generically gives rise to closely spaced opposite parity levels in low lying excited states. These parity doublets allow full polarization at low electric fields, a significant advantage for a range of applications such as precision measurement, quantum computation and quantum simulation. We have recently demonstrated a nearly closed cycling scheme leading to optical cooling and a one dimensional magneto-optical trap (MOT) of calcium monohydroxide (CaOH) molecules [1]. We have also demonstrated Sisyphus cooling on the symmetric top molecule (STM) calcium monomethoxide (CaOCH3) lowering a molecular beam temperature by an order of magnitude [2]. I will discuss these results and present the roadmap for the future of this technique.

[1] Baum, et. al., Phys. Rev. Lett. 124, 133201 (2020)

[2] Mitra, et. al., Science 369, 6509 (2020) 

Date and Time: 
Wednesday, January 13, 2021 - 12:00pm
Venue: 
Zoom ID: 987 676 025; +Password

QFARM Quantum Seminar Series presents "Towards quantum and classical light sources and transducers at any wavelength using nonlinear nanophotonics"

Topic: 
Towards quantum and classical light sources and transducers at any wavelength using nonlinear nanophotonics
Abstract / Description: 

Nanophotonics provides the unprecedented opportunity to engineer nonlinear optical interactions through the nanometer-scale control of geometry provided by modern fabrication technology. In this talk, I will outline our laboratory's efforts towards realizing the ability to engineer nonlinear interactions across a broad range of optical wavelengths, with a long-term goal of being able to develop methods and devices to access any optical wavelength of interest. Specific examples to be discussed include entangled photon pair sources, optical parametric oscillators, quantum frequency converters, and microresonator frequency combs.

Date and Time: 
Wednesday, December 2, 2020 - 12:00pm
Venue: 
Zoom ID: 987 676 025; +Password

Q-FARM presents "Lattice atom interferometry in an optical cavity"

Topic: 
Lattice atom interferometry in an optical cavity
Abstract / Description: 

Atom interferometers are powerful tools for both measurements in fundamental physics and inertial sensing applications. Their performance, however, has been limited by the available interrogation time of atoms freely falling in a gravitational field. I will describe our realization of an intra-cavity trapped atom interferometer with 20 seconds of coherence, which extends the interrogation time of spatially-separated quantum superpositions of massive objects by nearly an order of magnitude. I will discuss how this trapped geometry differs from traditional free-fall atom interferometers by allowing potentials to be measured by holding, rather than dropping, atoms.

Date and Time: 
Wednesday, November 25, 2020 - 12:00pm
Venue: 
Zoom ID: 987 676 025; +Password

Q-FARM presents "Wildcard error: Quantifying unmodeled errors in quantum processors"

Topic: 
Wildcard error: Quantifying unmodeled errors in quantum processors
Abstract / Description: 

Error models for quantum computing processors describe their deviation from ideal behavior and predict the consequences in applications. But experimental behavior is rarely consistent with error models, even in characterization experiments like randomized benchmarking (RB) or gate set tomography (GST). I show how to resolve these inconsistencies, and quantify the rate of unmodeled errors, by augmenting error models with a parameterized wildcard error model. Wildcard error relaxes the model's predictions, and the amount of wildcard error required (to reconcile the model with observed data) quantifies the rate of unmodeled errors. I'll demonstrate the use of wildcard error to augment RB and GST, and to quantify leakage.

Date and Time: 
Wednesday, November 18, 2020 - 12:00pm
Venue: 
Zoom ID: 987 676 025; +Password

QFARM Quantum Seminar Series presents "Millimeter-wave photons for quantum science"

Topic: 
Millimeter-wave photons for quantum science
Abstract / Description: 

Millimeter-wave frequencies (30-300GHz) provide a promising platform for quantum information technology at less explored but potentially beneficial length and energy scales. In this talk, I will discuss the advantages of the mm-wave band and describe our hybrid quantum system for entangling and inter-converting single mm-wave and optical photons using Rydberg atoms as mediators. I will go over our experimental progress and potential applications of our system for frequency transduction and quantum nonlinear photonics. To conclude, I will describe some applications of mm-wave photons we have explored for 2D nonlinear devices, photonic crystals, and twisted mm-wave Fabry-Perot cavities.

Date and Time: 
Wednesday, October 28, 2020 - 12:00pm
Venue: 
Zoom meeting ID: 987 676 025; password required

Q-FARM presents "Fast Optimization of Photonic Circuits for Automated Device Design"

Topic: 
Fast Optimization of Photonic Circuits for Automated Device Design
Abstract / Description: 

Photonic circuits are a promising platform for quantum computation and quantum communication: they don't require low temperatures or vacuum to operate and they can be built on a small chip. It would be wonderful to be able to design photonic circuits for any desired purpose, however in general this is a difficult task which we would much rather automate. In this talk I will present a new method to optimize photonic circuits (through differentiable simulation), which is about 100x faster than the previous state of the art. This allows us to automate the design of photonic devices, by starting with a random circuit and optimizing it until it achieves the desired behaviour. The added speed of our method allows us to design larger circuits and to achieve a much higher accuracy than it was previously possible. The talk is designed to be accessible to non-experts and will cover the basics of quantum optics, optical gates, photonic circuits and differentiable simulation.

Date and Time: 
Wednesday, September 30, 2020 - 12:00pm
Venue: 
Zoom ID: 987 676 025; +password

Q-FARM presents "Scaling-up single-photon quantum hardware towards quantum-information processing with a quantum advantage"

Topic: 
Scaling-up single-photon quantum hardware towards quantum-information processing with a quantum advantage
Abstract / Description: 

Semiconductor quantum dots embedded in photonic nanostructures offer a highly efficient and coherent deterministic photon-emitter interface [1]. It constitutes an on-demand single-photon source for quantum-information applications, enables single-photon nonlinear, optics and the constructing of deterministic quantum gates for photons [2]. We review recent experimental progress, and demonstrate that the current technology can be scaled up to reach quantum advantage [3] with the demonstration of near-transform-limited emitters in high-cooperativity planar nanophotonic waveguides [4]. The coherent control of a single spin in the quantum dot [5, 6] offers additional opportunities of generating advanced multi-photon entangled states [7]. We finally discuss how this emergent hardware may be applied in a resource-efficient manner, e.g., for constructing a one-way quantum repeater [8].

References

[1] Lodahl et al., Rev. Mod. Phys. 87, 347 (2015).
[2] Lodahl, Quantum Science and Technology 3, 013001 (2018).
[3] Uppu et al., Arxiv: 2003.08919.
[4] Pedersen et al., ACS Photonics (2020).
[5] Javadi et al., Nature Nanotechnology 13, 398 (2018).
[6] Appel et al., Arxiv: 2006.15422.
[7] Tiurev et al., Arxiv: 2007.09295.
[8] Borregaard et al., Phys. Rev. X 10, 021071 (2020).

Date and Time: 
Wednesday, September 23, 2020 - 12:00pm
Venue: 
Zoom meeting ID: 987 676 025; password required.

Q-FARM presents "Demonstrating different advantages in quantum processing"

Topic: 
Demonstrating different advantages in quantum processing
Abstract / Description: 

Quantum computing famously promises an exponential speedup in runtime for universal computation applications such as code breaking and simulation. However, it is possible to identify a number of processing tasks—perhaps of a different nature—for which other quantum advantages exist. I'll give an overview of three such tasks: a memory advantage in stochastic simulation; a communication advantage in distributed processing; and a resource advantage in transforming probability distributions. I'll describe the photonic experimental realisation of one or two of these.

Date and Time: 
Wednesday, September 16, 2020 - 3:00pm
Venue: 
Zoom Meeting ID: 987 676 025; +Password

Q-FARM Quantum Seminar Series presents "Restrictions on logical gates in quantum error correction"

Topic: 
Restrictions on logical gates in quantum error correction
Abstract / Description: 

The disjointness for stabilizer codes in quantum error correction is an algebraic quantity tied to the structure of the stabilizer generators of a code. It can be used to characterize the properties of different classes of logical gates, placing bounds on the level of the Clifford hierarchy attainable by constant depth circuits. This talk will introduce the notion of disjointness, highlight its usefulness with several examples, and posit open questions for which the disjointness may be useful in addressing.

Date and Time: 
Wednesday, September 2, 2020 - 12:00pm
Venue: 
Zoom ID: 987 676 025; +password

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