@heather word of advice: don't break the crystal... Be careful with it. Be so unbelievably careful that everything else feels totally careless in comparison, despite 'everything else' involving extreme levels of precision
Seriously, we had a broken crystal - the level of care after that was insane
So you need a bottle of compressed air so that no dust gets on whatever the crystal's on top of - this is the most important thing (a bit of dust can crack the crystal)
It doesn't actually matter if the sides of the crystal are perfectly clean (so long as they're dust, dirt etc. free so they don't crack), so long as the bit that the light's going through is clean
(if that makes sense?)
@heather Hmm... We just keep them in the small plastic boxes they come in
Yeah, there's also a difference between keeping something in a box in a cupboard that's rarely opened in a well sealed physics lab in a physics department and keeping it in your house :P
@heather Physics lab conditions? :P I don't actually know at this point, other than to say that the exact properties of the crystal vary with temperature, which is another experimental parameter, although the crystal itself is unharmed between at least around 10-100 (ish) degrees C
@akinuri The 3D one looks pretty decent in terms of realism :)
there's a closet in the lab that i'll maybe store the crystals in, and i'll make sure they're wrapped in a soft cloth, probably in the box they're sent. i might as well get a simple desiccant too, just to be safe.
@heather From a graphical perspective, this effect is called pinch. What I'm wordering is does mass also twirl space? I mean, the sun for example. It bends the space around it, but it also spins. Does this spin (besides its mass) also affect the space? A twirl example: i.stack.imgur.com/OTofy.png
To be honest, I don't even think we actually use any for the crystals - the box they come in might be good enough, or the lab might be good enough... (we do use them for other stuff though)
@Mithrandir24601 Not really. The primary effect of mass stationary on space-time is on the time-like component. This diagram continue the incorrect impression that it is the space-like part bends.
I've been checking the pages related to "Kerr metric" and "Frame dragging". I suppose these from wiki confirm that rotation affects the distortion.
"A stationary field is one that is in a steady state, but the masses causing that field may be non-static, rotating for instance."
"They predicted that the rotation of a massive object would distort the spacetime metric, making the orbit of a nearby test particle precess. This does not happen in Newtonian mechanics for which the gravitational field of a body depends only on its mass, not on its rotation."
@DanielSank According to Wiki: "The site ranked third in a 2002 study performed at Stanford University about trust and credibility, just behind Amazon and Barnes & Noble", so fair enough I suppose...
Here's the question: A baseball and a ball of clay are approaching each other. The mass of the baseball is 145 g and it is moving due west 5 m/s at 180 degrees. The ball of clay is 290 g and it is moving northwest at 135 degrees at 4 m/s. What is the magnitude of their combined velocity after they collide and stick together?
I first tried to find velocity in the x direction, then velocity in the y direction, and use the Pythagorean theorem to find total magnitude. I got 1.71 m/s. Why is this wrong? What should I be doing instead?
oh, also @DanielSank - I tried getting the audio fixed earlier today... It can be done, but it would take me many tens of hours :/ and it would sound utterly horrible, so I had to give up on it :/ Lesson learned for the future...
@DanielSank Sure! It'll probably be to slightly different people (new cohort in, half the cohort I'm in won't be in Bristol any more) and it might take me a few weeks, but it'll happen! Of course, if you ever find yourself in Bristol...
Or even the UK... (the Uni is happy to pay a limited amount of travel expenses, but unfortunately can't afford to bring someone all the way from America)
hello guys, I have a question: -- for a 13 sided regular polygon with 13 equal charges (q) on each vertex what is the net force on a charge (Q) placed at the center of the shape? I've learned that it would be zero, but why is that? can I come to this conclusion without vector addition of the forces?
@Mithrandir24601 I have a possible offensive question, but I promise it's just my ignorance: I keep hearing that optical quantum computing is really hard and inefficient. Are there any outstanding problems that appear solvable that would make the field less scary?
and setting it up to do multiple qubits will be difficult, i think.
the short answer is, i couldn't really tell you how well it will work.
i'm still trying to figure out the mathematical operation SPDC performs on the polarization of a photon.
that's really why i think it probably won't work - i'm really inexperienced in experimental physics and quantum computing and optics and quantum mechanics (i.e., all the things).
when i figure out the mathematical representation for SPDC, i can start figuring out how to construct gates, how to create a certain circuit, and so forth.
@DanielSank So, if someone could build a good, deterministic single photon source that can be multiplexed or is easily copyable (to get exactly the same wavelength photons), that would pretty much be problem solved. Alternatively, we need a few more dB of squeezing to do continuous variable...
@heather first hint: optical QC has lots of loss involved. Gates make loss issues even worse, so why would you want to implement lots of gates? Is there an alternative model that doesn't use as many gates, yet is equivalent? (hint: I'm asking the question, so...)
@DanielSank Not everyone, just nearly everyone - some of us are beginning to look into simulating on quantum chips e.g. I'll be doing a little bit on lossy systems in the hope we get some insight that helps chip design (and other, less relevant things)
@heather Ah, sorry - I'm asking: Is there an alternative to the gate model of quantum computing that's entirely equivalent, yet easier to implement in photonics?
