Tag Archives: photons

QM 101: Fun with Photons

Last time I explored the quantum spin of photons, which manifests as the polarization of light. (Note that all forms of light can be polarized. That includes radio waves, microwaves, IR, UV, x-rays, and gamma rays. Spin — polarization — is a fundamental property of photons.)

I left off with some simple experiments that demonstrated the basic behavior of polarized light. They were simple enough to be done at home with pairs of sunglasses, yet they demonstrate the counter-intuitive nature of quantum mechanics.

Here I’ll dig more into those and other experiments.

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QM 101: Photon Spin

Earlier in this QM-101 series I posted about quantum spin. That post looked at spin 1/2 particles, such as electrons (and silver atoms). This post looks at spin in photons, which are spin 1 particles. (Bell tests have used both spin types.) In photons, spin manifests as polarization.

Photon spin connects the Bloch sphere to the Poincaré sphere — an optics version designed to represent different polarization states. Both involve a two-state system (a qubit) where system state is a superposition of two basis states.

Incidentally, photon polarization reflects light’s wave-particle duality.

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Thanks for Patterns

The Thanksgiving holiday we celebrate here in the USA has some unfortunate overtones regarding its colonial origin. Still, the idea of a festival of thanks is an ancient one — thanks for a good harvest or a good hunt. Or, in our case, thanks for helping us not die last winter.

As with Christmas or the Copenhagen interpretation, we tend to take a “shut up and calculate!” approach to the holidays. “Shut up and shop!” in the case of the Winter Solstice, and “Shut up and give thanks!” today.

One thing we can be very thankful about is patterns…

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BB #61: News Bubbles

I have a growing list of links to articles that catch my eye, things I’d like to post about (for whatever reason). But there’s a tension between posts based on lists of links or draft posts or idea files versus posts based on what I’m currently thinking about.

I seem to feel the latter isn’t enough, that I need a reserve for “lean times” — which never happen. More and more, I post when something strikes me as worth the effort. The “idea pile” seems almost like homework.

Anyway, here are some things that recently caught my eye.

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Time and Two Doors

In the last week or so I read an interesting pair of books: Through Two Doors at Once, by author and journalist Anil Ananthaswamy, and The Order of Time, by theoretical physicist Carlo Rovelli. While I did find them interesting, and I’m not sorry I bought them (as Apple ebooks), I can’t say they added anything to my knowledge or understanding.

I was already familiar with the material Ananthaswamy covers and knew of the experiments he discusses — I’ve been following the topic (the two-slit experiment) since at least the 1970s. It was nice seeing it all in one place. I enjoyed the read and recommend it to anyone with an interest.

I had a little trouble with the Rovelli book, perhaps in part because my intuitions of time are different than his, but also because I found it a bit poetic and hand-wavy.

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Wireless World

At work, more than a decade ago, Wi-Fi let us take our laptops to meetings or the cafeteria or even nearby outside. At home, while the old laptop couldn’t hold a connection, so remained tethered to the DSL modem, the new laptop does just fine. So does the iPad, going on two years now.

The new laptop uses a wireless keyboard and mouse. And I’ve been using wireless headphones to watch TV for a year or so. It’s really nice having no wires for devices I’ve used for so long in tethered form. Of course cell phones started it quite a few years ago.

It all does seem to come with a new set of (minor) headaches, though!

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