Friday, July 12, 2019

First Image Of Entangled Photons

We have the first image ever of photons in an entangled state. You may read the actual paper at the Science Advances page.

Of course, you can't tell that there is any entanglement going on just by looking at the image shown. You have to read the entire thing to see why there is a clear violation of Bell-type inequality here, or more specifically, the CHSH inequality that was meaning measured.

Neat stuff!


Friday, June 28, 2019

150 Years of the Periodic Table

Happy 150th Birthday, Periodic Table! You don't look a day over 149!


Wednesday, May 29, 2019

How Do You Detect A Neutrino?

Another Don Lincoln video, and this time, it is on a topic that I had a small involvement in, which is neutrino detection.

My small part was in the photomultiplier photocathode used for detection of Cerenkov light that is emitted from such a collision between the "weak boson" and the nucleus. We were trying to design a photodetector that has a large surface area as compared to the current PMT round surface.

In any case, this is a good introduction to why neutrinos are so difficult to detect.


Friday, May 24, 2019

Charles Kittel

Physicist Charles Kittel passed away this past May 15th, 2019.

This is one of those names that will not ring a bell to the public. But for most of us in the field of condensed matter physics, his name has almost soared to mythical heights. His book "Introduction to Solid State Physics" has become almost a standard to everyone entering this field of study. That text alone has educated innumerable number of physicists that went on to make contribution to a field of physics that has a direct impact on our world today. It is also a text that are used (yes, they are still being used in physics classes today) in many electrical engineering courses.

He has been honored with many awards and distinctions, including the Buckley prize from the APS. He may be gone, but his legacy, influence, and certainly his book, will live on.


Sunday, May 12, 2019

The Geekiest T-Shirt That I've Ever Bought

I just had to get this one. I found this last week during the members night at Chicago's Adler Planetarium.

The people that I were with of course knew that this is referring to "force", but they didn't get the connection. So I had to explain to them that Newton's 2nd law, i.e. F=ma can be expressed in a more general form, i.e. F = dp/dt, where p is momentum mv. Thus

F = d/dt (mv)

Of course, I'm not surprised that most people, and probably most of Adler's visitors, would not get this unless they know a bit of calculus and have done general physics with calculus. Maybe that was why this t-shirt was on sale! :)

Maybe I'll wear this when I teach kinematics this Fall!


Friday, May 10, 2019

Table-Top Laser Ablation Unit

I was at the Chicago's Field Museum Members Night last night. Of course, there were lots of fascinating things to see, and wonderful scientists and museum staff to talk to. But inevitably, the experimentalist in me can't stop itself from geeking out over neat gadgets.

This was one such gadget. It is, believe it or not, a table-top laser ablation unit. It is no more bigger than shoe box. I was surprised when I was told what it was, and of course, I wanted to learn more. It appears that this is still a prototype, invented by the smart folks at ETH Zurich (of course!). The scientist at Field Museum uses it to do chemical analysis on trace elements in various objects in the field, where the trace elements are just too minute in quantity that x-ray fluorescence would not be effective.

Now, you have to understand that typically, laser ablation systems tend to occupy whole rooms! It's job is to shoot laser pulses at a target, causing the evaporation of that material. The vapor then typically will migrate to a substrate where it will form a thin film, or coat another object. People use this technique often to make what is known as epitaxial films, where, if suitably chosen, the new film will have the same crystal structure as the substrate, usually up to a certain thickness.

So that was why I was fascinated to see a laser ablation kit that is incredibly small. Granted, they don't need to do lots of ablating. They only need to sample the vapor enough to do elemental analysis. The laser source is commercially bought, but the unit that is in the picture directs the laser to the target, collects the vapor, and then siphon it to a mass spectrometer or something to do its analysis. The whole thing, with the laser and the analyzer, fits on a table top, making it suitable to do remote analysis on items that can't be moved.

And of course, as always, I like to tout of the fact that many of these techniques originate out of physics research, and that eventually, they trickle down to applications elsewhere. But you already know that, don't you?


Saturday, May 04, 2019

Why Does Light Bend When It Enters Glass?

Don Lincoln tackles another "everyday" phenomenon. This time, he tries to give you an "explanation" on why light changes direction when it goes from one medium to another, and why some of the more popular explanation that have been given may be either incomplete, or wrong.

Certainly, any undergraduate physics student would have already dealt with the boundary conditions using Maxwell's equations, so this should be entirely new. However, he skipped rather quickly something that I thought was not handled thoroughly.

The continuity of the parallel component of E to the boundary is fine. However, Lincoln argued that the reason why the perpendicular component of the F field is shorter in glass is due to the polarization of the material, and thus, the sum of the light's E-field and the E-field from the polarization will cause the net, resultant E-field to be shorter.

But if the material's polarization can affect the perpendicular component, why doesn't it also affect the parallel component? After all, we assume that the material is isotropic. This, he left out, and at least to me, made it sound that the parallel component is not affected. If this is so, why?


Monday, April 29, 2019

How Beauty Leads Physics Astray

Sabine Hossenfelder is probably doing a "book tour", since this talk certainly addressed many points that she brought up in her book.

As I've said many times on here, I don't disagree with many things that she brought up. I find the trend of foundational physics to even think about discarding experimental verification to be very troubling. I'm just glad that the field that I'm in is still strongly experimental.


Wednesday, April 10, 2019

First Images of a Black Hole

After a week of rumors and build-up, the news finally broke and it is what we have been expecting. It is the announcement that we finally have our first image of a black hole.

The first direct visual evidence of a black hole and its “shadow” has been revealed today by astronomers working on the Event Horizon Telescope (EHT). The image is of the supermassive black hole that lies at the centre of the huge Messier 87 galaxy, in the Virgo galaxy cluster. Located 55 million light-years from Earth, the black hole has been determined to have a mass 6.5-billion times that of the Sun, with an uncertainty of 0.7 billion solar masses.

You can actually read the papers that were published related to this announcement, so you can find a lot more details there.

Well done, folks!!


Wednesday, March 27, 2019

How Do You Make Neutrino Beam?

This new Don Lincoln's video is related to the one he did previously on the PIP-II upgrade at Fermilab. This time, he tells you how they make neutrino beams at Fermilab.


Monday, March 25, 2019

CP Violation in D Meson Decay

LHCb is reporting the first evidence of CP violation in the decay of D meson.

The D0 meson is made of a charm quark and an up antiquark. So far, CP violation has only been observed in particles containing a strange or a bottom quark. These observations have confirmed the pattern of CP violation described in the Standard Model by the so-called Cabibbo-Kobayashi-Maskawa (CKM) mixing matrix, which characterises how quarks of different types transform into each other via weak interactions. The deep origin of the CKM matrix, and the quest for additional sources and manifestations of CP violation, are among the big open questions of particle physics. The discovery of CP violation in the D0 meson is the first evidence of this asymmetry for the charm quark, adding new elements to the exploration of these questions.

If confirmed, this will be another meson that has exhibited such CP violation, and adds to the argument that such symmetry violation could be the source of our matter-antimatter asymmetry in this universe.

CP violation is an essential feature of our universe, necessary to induce the processes that, following the Big Bang, established the abundance of matter over antimatter that we observe in the present-day universe. The size of CP violation observed so far in Standard Model interactions, however, is too small to account for the present-day matter–antimatter imbalance, suggesting the existence of additional as-yet-unknown sources of CP violation.