Generating and manipulating single photons with semiconductor devices

Introduction

In this section, the speaker introduces himself and his lab. He also talks about the objective of his work.

Speaker's Introduction

• The speaker thanks the organizers for doing a beautiful job organizing the first quantum technology conference in Paris.

• The speaker introduces himself and his lab, which is located in the center of nanoscience and nanotechnology.

• The speaker talks about how they fabricate chips that are electrically controlled to provide tools for optical quantum technologies.

Objective of Work

• The speaker explains that their objective is to generate and manipulate light at a single quantum level to provide tools for optical quantum technologies.

Optical Quantum Technologies

In this section, the speaker discusses optical quantum technologies and their importance in various applications such as quantum communication, quantum networks, and quantum computing.

Importance of Single Photons

• Single photons play a central role in many applications such as quantum communication.

• If you want to go beyond point-to-point communication, you will need single photons.

• There are different architectures for building quantum networks based on either quantum memory or measurement-based quantum repeaters.

Photonics in Quantum Computing

• Light has been explored for use in quantum computing applications by many groups worldwide.

• Photonic qubits have managed to untangle and manipulate more than two qubits typically four to ten photonic qubits have been manipulated.

• An optical computer would run at room temperature for most parts with easy implementation of single-qubit gates.

Quantum Light Sources

In this section, the speaker discusses the need for quantum light sources and the ideal properties of a single photon source.

Need for Quantum Light Sources

• To build an optical quantum computer, we need quantum light sources.

• Efficient photon-photon gates are required for quantum relays, computation, and teleportation.

Ideal Properties of Single Photon Source

• Ideally, each pulse should have exactly one photon no more than no less.

• A single atom or two-level system has been known to scatter only one photon at a time.

Optical Emission and Quantum Purity

In this section, the speaker discusses how the emission of photons is affected by the coupling to a crystal and how they were able to suppress phonon sideband emission in their quantum gravity system.

Coupling to Crystal

• The artificial atom is coupled to the vibration of the crystal, resulting in a spectrum that is no longer a sharp emission line.

• The emission includes photon plus non-English absorption of a phonon plus emission of a photon.

• In their quantum system, 90% of the emission is intrinsic while only 10% is due to coupling with the crystal.

Suppressing Phonon Sideband Emission

• They used cavity QED to get rid of fun on assisted phenomena and suppress phonon sideband emission.

• This helped them achieve high quantum purity in their system.

• They showed experimentally that they were able to suppress up to a very large extent fun and assisted phenomena.

Charge Noise and Electrical Environment

In this section, the speaker discusses how they got rid of charge noise in their quantum dot environment by using semiconductor technology.

Charge Noise

• Even though their material was extremely pure, there was always a probability that there would be residual charge around the emitter due to traps.

• This created an electric field that interfered with their quantum dots.

Creating Clean Electrical Environment

• They included a quantum emitter in an iodine pin diode structure where they could apply an electric field.

• This allowed them to sweep out charges away from their emitter and create a clean electrical environment for their quantum dots.

• They improved their technology by keeping 1D ridges that connect a cavity to a bigger frame where they can define electrical contacts which still control the position of the emitter very precisely.

Quantum Dot Environment

In this section, the speaker discusses how they improved their technology to create a quantum dot environment and measure its efficiency.

Measuring Efficiency

• They measured the input and output coupling efficiency for the light that goes in and out of their device.

• They were able to detune the quantum dots and remove them from the system, allowing them to measure the Q factor.

• The Q factor was through tens of thousands at best.

• They were able to turn the voltage and bring the quantum dot in resonance with the cavity mode, resulting in a huge signal showing a very high-efficiency single photon emission.

Introduction

The speaker introduces the topic of natural atom and what has been done with it.

Natural Atom

• Natural atom is introduced.

Comparison with Single Photon Sources

The speaker compares devices made with natural atom to single photon sources.

Ideal Single Photon Source

• The ideal single photon source is described in terms of indistinguishability, brightness, and optical contact energies.

Welded Single Photon Sources

• Welded single photon sources are discussed as being easy to use at room temperature and having demonstrated many beauty from the optical quantum protocols. However, there is a limitation in that they are not true single photon sources but rather behave statistically as such.

• Strategies have been developed to try to go beyond this limitation using multiplexing of these sources which is under development.

Progress Made by Quantum Community

• Progress made by the quantum community in producing efficient single photons with a single quantum dot is discussed. An order of magnitude increase in brightness for the same quality in terms of quantum purity was achieved which is significant because efficiency scales exponentially with brightness power to N where N represents all the protocols you want to implement with single photons.

• The first experiment that has been done to prove this was button sampling which showed that predicting the output of such network is very hard classically and requires something like 30 to 50 photons. It seems that you could demonstrate quantum supremacy or some kind of calculation that you couldn't do on a classical computer using this method.

Deterministic Fat and Fat and Gate

The speaker discusses the need for a deterministic fat and fat and gate.

Making a Gate Between Two Photons

• The current method of making a gate between two photons which are particles that don't interact is discussed. Quantum interferences are used to coalesce identical particles at the output of a beam splitter. However, the gate operates only 10-15% of the time which is not sufficient for quantum computing.

Using Single Atoms as Nonlinear Mediums

In this section, the speaker discusses how a single atom can be used as a nonlinear medium at a single photon level to make efficient 10 photon gates.

Single Atom Nonlinearity

• A single atom can be used as a nonlinear medium at a single photon level.

• The non-linearity is observed in continuous wave at a photon number inside the cavity of four ten to the minus five.

• To use this device to make a gate, it needs to operate on light pulses because it's really light pulses that need to be manipulated to make gates etc.

Reflectivity Measurements

• Reflectivity measurements are taken using a curve and show that the reflectivity dip is the cavity.

• Photon numbers are defined so that they go from high reflectivity to low reflectivity.

• The transition happens for a threshold of 0.3 photon patters, evidencing nonlinear sensitivity at a single photon level.

Second Order Correlation Measurement

• A hum g2 measurement is done for the same parameters and shows that most of the reflected light from the device is very much single for tonight.

• The g2 is point 35 which is well below point 5 and shows actually that most of the reflected light from my device is very much single for tonight.

Conclusion and Perspective

In this section, the speaker concludes by discussing future work on making quantum sources better and producing exactly the same quantum right. They also mention spin currents time as being something like one microsecond and how it can be manipulated in the tens of Pico seconds.

Future Work

• Candela has been created to provide single photon sources and official quantum light sources.

• The brightness can be improved by changing the excitation scheme playing a bit open the parameters.

• Different sources producing exactly the same quantum right are being worked on.

Spin Currents Time

• The spin of a carrier in a quantum dot could be a very nice qubit that to do a very long term quantum memory because the spin currents time is something like one microsecond but if you look at the ratio to the spinning from the spin currents time to the spin manipulation time you see that you have quite up space.

Spin State and Photon Entanglement

In this section, the speaker discusses the spin state and photon entanglement. They mention that they had their first measurement three years ago where they rotated in the light of the polarization of the light by plus minus six degrees depending on the spin state. They also discuss how they are bringing these numbers to a higher value to achieve spin-photon entanglement.

• The speaker mentions that with spin-photon entanglement, it is possible to do spin-spin photon-photon gates.

• They discuss how there are nice protocols that they now want to implement using a spinner again but this time to generate single photons and using spin manipulation.

• The speaker talks about creating linear crystal states of similar patterns and how if they get there, there are a lot of possibilities for measurement-based quantum communication measure and quantum computing.

Latest Developments in Quantum Technology

In this section, the speaker talks about the latest developments in quantum technology.

• The speaker mentions that if you are interested in the latest development not only in their group but in the quantum community and single photon sources, they have written a review paper in nature nanotechnology last year.

• They talk about scaling up particle quantum technologies and work towards photon gates.

Acknowledgments

In this section, the speaker thanks their group members for their contributions.

• The speaker thanks their wonderful group for their contributions.

• They mention Lorenzo de Santis who was in charge of single photon non-linearity.

• The speaker lists other members who contributed to spin physics such as Rohit Franco.

• They encourage anyone interested to discuss more details with them or someone from their team.

Questions from Audience

In this section, the speaker answers questions from the audience.

• The first question is about quantum dots and whether they are all different and need to be tuned electrically. The speaker responds that they can tune electrically to some extent but not much.

• The second question is about the bandwidth of the fully limited wave packet generated. The speaker responds that it's around 1 gigahertz.

• The third question is about indistinguishability and yield. The speaker explains that their limit is testing the quantum purity in the frequency basis when they do this measurement, not in the photon number basis. They also mention that for two different dots, the state of the art is around 86 percent in terms of indistinguishability.

• The fourth question is about how many pillars are needed to build before having one that performs nicely. The speaker explains that with their technology, all quantum dots are exactly at the center and have good spectral tuning so all pillars work okay. They also mention that in one run of technology, they can fabricate 40 sources.

Limitations of Quantum Dot Brightness

The speaker discusses the limitations of quantum dot brightness and possible solutions.

Decreasing Q Factor for Higher Brightness

• Decreasing the Q factor can increase brightness.

• Out coupling efficiency is currently limiting source to 70%.

• Compromise is less efficient suppression of fun and silence, leading to lower indistinguishability.

• Other ideas are being explored to improve brightness.

Enhancing Energy Difference Between Two States

• Enhancing energy difference between two states is another path to increasing brightness.

• Excitation and emission happen on the same line but not at the same time.

• Changing excitation frequency slightly can influence coherence properties of emission.

Influence of Frequency and Phase Evolution on Emitted Photon Coherence

The speaker discusses how changing frequency or phase evolution can influence coherence properties of emitted photons.

• By changing frequency or phase evolution, it's possible to influence coherence properties of emitted photons.

• Results have been obtained but not presented in this talk.

I understand the instructions. Thank you for providing them. I will follow the given structure and format to create a clear and concise markdown file.

Asking Alan Again

In this section, the speaker talks about asking Alan again about something.

Asking Alan Again

• The speaker mentions that they have asked Alan again about something.

• It is not clear what exactly they have asked him about.

This is a very short section with only two bullet points as there was not much information provided in the transcript.