I did experiments about quantum computing using neutral atoms when I was graduate school student.
So, I’m not familiar with photonic quantum computer.
But recently, I get interested with Borealis in Xanadu.
I’d like to compare Borealis with neutral atom based quantum computer.
What is the coherence time of Borealis?
And What can you describe the gate speed of Borealis?
Interesting question. My initial guess is that the notion of coherence time and gate speed doesn’t fit within the description for what the hardware underpinning Borealis is. However, I’ve asked an expert for clarification and I will get back to you once I hear back from them . Sit tight!
Thank you for your question! It’s great that you’re interested in photonic quantum computers and Borealis. Let me first add some context and useful resources where you can learn more about Xanadu’s computers. Then I’ll answer your specific question.
First of all, photonic quantum computers can have many different architectures. At Xanadu our fault-tolerant architecture (the computers we’re in the process of building) is based on measurement-based quantum computing. This is not the same architecture as Borealis or our previous generation of computers (X-series). Borealis was a huge milestone and a key step for us to develop the technologies we needed to build into our architecture. However, our architecture goes well beyond Borealis.
If you want to learn about photonic quantum computing, our demo on this topic is the best place to start. If you want to learn about measurement-based quantum computing you can go to our demo on the topic. If you prefer videos I recommend the one on How Xanadu’s Photonic Quantum Computers Work and the one on How to Build a Quantum Computer with One Million Qubits. They’ll give you a very nice overview of how our photonic quantum computers and our architecture works. Note that there are other photonic architectures too! Other companies and research groups have different approaches. If you want to learn specifically about Borealis you can check out our video, our blog post, the paper published on nature, and our tutorials on it.
Now, going specifically into the questions you asked, we need to look into the appropriate comparison, not the direct equivalent.
Borealis creates pulses of light at a frequency of 6MHz. Each rectangular pulse has a duration of 3ns. Each of these pulses travel through fiber optics from the source, through the gates, through the delay loops, into the demultiplexor, and finally into the detectors for measurement. Since we’re working with light this is extremely fast and our setup allows the light to maintain its properties all the way up to measurement. In photonics the challenge isn’t in coherence times but instead in photon loss, which is a completely different metric. The speed of the gates in this case was I guess 6MHz since you could individually program each gate for each mode.
The nature paper has a lot of technical details so it’s a good resource to dig into if you want more detailed information. It also includes a lot of comments on loss.
Please let me know if you have any additional questions and I hope you keep up your interest in photonics!