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Hi, my name is Andrew Cameron. I'm a research associate at Fermilab's Quantum Networking Team. I'd like to give you a tour of my lab today. We're at the D0 building. Come on inside. In Fermilab's Quantum Network, we look to connect different quantum devices through fiber optic cables. We send single photons for protocols such as entanglement distribution, quantum teleportation, and entanglement swapping. Quantum networks have three main applications, two of which are realizable today. There's quantum cryptography, which helps with secure communication between nodes.
There's quantum sensing for measurements that can benefit from distributed entanglement. And our large-scale goal is to build a quantum internet, a global interconnected system for quantum devices across the planet. To start the tour, I'll show you our entangled photon sources. Each of these breadboards on this table is a different photon source. We start with a classical laser that has no pulse structure, but we're going to need to modulate it to create pulses because on our table, the time of arrival of a photon determines its state. This modulation procedure is initiated by a custom Fermilab FPGA made by the QICK group at Fermilab.
We then take that modulation, apply it to the laser, and get a pulse structure classically. Now that we have classical pulses, it's time to create photons. Here we have nonlinear optical crystals, where photons will come in and split into two entangled photons in a process called down conversion. Their energy adds up to the photon that created them, and they're created at the same moment in time, which is where the entanglement arises.
Now that we have our photons generated, it's time to send them to the network further down the table. Further down the table, we send our photons through these long fiber spools. For quantum networks, it's important to be able to connect things long distance, but we need to make sure it's working first. So in the lab, we have 5 kilometers in this case of fiber where the photons can travel and emulate this long distance. Our experiment involves multiple nodes. On Fermilab campus, we currently have two different nodes, the FCC and D0.
We have connections with Argonne National Lab and Northwestern University in Chicago. A longer term goal is to connect even further. If we go down south to UIUC, I think that's about 200 kilometers. These experiments get more challenging as the distance increases, and on tables like this, where we can emulate the distance, we get an understanding of how those lengths change over time. In some cases, two photons might need to arrive at a beam splitter at exactly the same time to interfere. So the length and the temperature control of these fibers is very important for these experiments. After our photons have traveled long distances, it's time to detect them.
Our detection devices are called superconducting nanowire single photon detectors. Here we have a Quantum Opus detector, and our FCC lab, our collaborators at the Jet Propulsion Lab, have given us even faster detectors with 10 picosecond resolution. These detectors are very good at understanding when the photon arrives with incredibly accurate timing precision, which is important when the quantum information is stored in the arrival time of the photon. And last stop, we'll show you the analysis software that shows us what these time bins look like. Now that our photons have been detected, the first thing to do is time stamp them.
We have a device which relative to a clock we send can give time values for each of these occurrences. This data is fed into a computer, and we can analyze it with the software from our friends at Caltech. They have given us a way to visualize what these count statistics look like. The x-axis on these diagrams is time. If we look at the top row, for example, this is the output of a single detector. We see that we have these pulses of time stamps every 5,000 picoseconds, which is the rep rate of our laser, and the different rows correspond to different detector outputs.
Lastly, in quantum optics, it's very important to be able to compare the time of arrival of two different detectors. So here we can define these red lines, which allow us to zoom in on specific instances in time, and we can do coincidence measurements and say that we got a photon in this detector at the same time, that we got a photon in another detector. Our long-term goal for this lab is to do a long-distance entanglement swapping experiment. If you have two entangled photon sources, like the ones I showed behind me, you can take a photon from each of those sources and interfere them on a beam splitter.
If you look at measurements correctly, you can now transfer the entanglement from these sources to the two photons that have never interacted. This is a key enabling technology for long-distance quantum communication experiments, and that's why it's our goal to be able to do this procedure as long-distance as possible. Thank you. I hope you enjoy the tour of the Fermilab quantum network.
