This paper presents a thorough theoretical treatment (with some bonus new experimental results) of our recent demonstrations of phase measurement algorithms which variously beat the standard limit and achieve the fundamental limit of precision. We show how to do this without resorting to entangled states, both with and without adaptive measurements.
We were (or more specifically, our theory collaborator Prof. Howard Wiseman was) invited to write a paper for IEEE Journal of Selected Topics in Quantum Electronics. Here we describe several of the experiments recently taking place in our (or more specifically, Prof. Geoff Pryde's) laboratory, of which Howard is an integral part. It discusses the recent work on phase measurement, with some bonus theoretical details, as well as touching briefly on some soon-to-be-published work on adaptive quantum state discrimination.
Following up our previous publication, here we theoretically prove and experimentally demonstrate a quantum control algorithm to measure an optical phase at the fundamental Heisenberg limit of precision without entangled states or adaptive mesurements. We also demonstrate a simplified adaptive protocol with accuracy surpassing standard techniques.
This post marks the day of my first publication in a scientific journal. And it just so happens to be in Nature. For those not in the know, Nature is one of the highest-tier multidisciplinary journals in the world (if not the highest-tier: ongoing competition with Science makes that perennially debatable). As you can imagine, I'm pretty chuffed about that.
In this work, we developed and experimentally demonstrated an algorithm for phase measurement utilizing techniques from quantum control and quantum computation to achieve efficiency at the fundamental limit, better than any classical method, without requiring quantum entanglement. A thousand thanks to my coauthors and colleagues who gave me the opportunity to be a leading part of this project.
After some expensive failed experiments in building a dedicated MythBox out of a MiniITX form factor system, I decided what I really wanted was a quiet machine that would do everything. That is, a machine I could just leave on all the time, downloading, serving, processing, recording... anything. The problem I had in attempting to do this with my regular desktop machine was that my machine was (a) situated only a couple of metres from my bed, and (b) loud. Loud enough to make sleeping anywhere near it uncomfortable.
With the new goal to fix the problem of noise, I bought a new case on my way back from visiting my parents over the Christmas break: an Antec P180. I also bought a new, quiet PSU: an Antec TruePower Trio 550W.
As I work during the day (starting a new year in the lab), all of the following happened over several consecutive nights. I had to spend a couple of nights disassembling everything from the old case and reassembling everything in the new case. It wasn't until some days later that I was finally able to check whether my machine had not only survived the trip home (which, honestly, was [...]
It started with an impulse purchase. I was browsing Harvey Norman for one reason or another (I was probably in there to buy some overpriced printer ink) when I stumbled across the TV tuner card aisle. I had been digital-TV-curious for a while—this at a time when digital-TV was still fairly recent—and I was in a buying mood, so I bought a single-tuner DviCo PCI HDTV card. It took a bit of effort to get the software right, and I had to also get myself a long TV aerial cable, but it wasn't too long until I got working TV on my computer.
It was at this point that strange and wonderful ideas began to form in my head. Words like “MythBox” and “PVR” and “TiVo” coalesced, loitered around menacingly, and formed gangs that beat up other words like “easy”, “sensible” and “cheap”.
I considered for a moment what I already had to work with. I had an nVidia video card with, supposedly, video out function. I say “supposedly” because, at the time that I tried it, nVidia's Linux drivers were a bit thin on this particular front. TV out would kinda-sorta work, I think, but probably wouldn't [...]
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