Some of the strangest characteristics of quantum theory can be demonstrated by firing a photon into an interferometer

**** QUANTUM SHORTS 2019/2020: HONOURABLE MENTION**

Alice was beginning to wish that she hadn’t been *quite* so curious about why a rabbit would be carrying a pocket watch,* and *that she* *hadn’t followed the White Rabbit down that rabbit hole to find out. But she had been, and she did, and now she found herself hopelessly lost in this dark wood, not knowing which way to go.

Feeling sorry for herself, she sighed and sat down beneath a big tree to think.

“Proposition 1,” she began. “A path goes from point A to point B. Proposition 2: I am at point A. Proposition 3: I wish to get to point B. Conclusion: I must find a path from A to B.”

Feeling very satisfied with herself, she looked around. “But there *are* no paths in this forest!” she said, and sighed again.

But when she looked down again, she saw a path that began at her feet and meandered away through the trees.

“I’m certain *that *wasn’t there before,” she thought.

But under the axiom that a path must invariably lead somewhere, she decided to follow it.

This particular path however seemed to have never heard of that axiom, showing no inclination to go anywhere at all! It simply looped around, and tied itself into knots, and pretty soon Alice found herself right back at the very same tree she had started from.

Only now there was a large gray cat sitting in it.

Looking up at the Cat, she began, "Sir, would you tell me, please, which way I ought to go from here?"

"That depends a good deal on what you mean by the words 'way', 'go', and 'here'," said the Cat.

Unperturbed, Alice tried another question: "What sort of people live around here?" and followed it with philosophically precise definitions of ‘here’, ‘people’, ‘live’ and, just to be sure, ‘what’, ‘sort’ and’ around".

Satisfied, the Cat replied, "In *that *direction," waving a paw, "lives a Hatter, and in *that *direction," waving the other paw, "lives a March Hare. Visit either you like; they're both postmodern philosophers."

Alice looked in the directions that the Cat had indicated. "But I don't want to go among postmodernists!" she thought.

Turning back towards the tree, she was surprised to see there was now an orange cat sitting where the gray cat had just been.

"Could you tell me where the gray cat went?" Alice asked politely.

The Cat sniffed and replied, "I’ve no idea. I've been sitting here, by myself, all day and, as you can see, I am an *orange* cat! I have always *been* an orange cat! I always *will* *be* an orange cat!"

Then, just as he was about to start into his familiar recitation of how his ancestors had come over with William of Orange, which he regularly bores all his friends to death with, he changed into a white Persian cat, and then into a Norwegian Forest cat, and then into a black-and-tan Tabby.

Alice, feeling proud of herself (for they had just covered the new theories coming from the Continent in her lessons the previous week), realized then that he was actually a *Schroedinger *cat. "Your wave function," she explained, "consists of a superposition of different eigenstates of, I suppose, a 'Catness' operator." Although she *did *wonder why his wave function, after collapsing to an eigenstate, didn't stay collapsed like a proper wave function.

"Perhaps it's artistic license," she thought.

Then, to show off her new knowledge, she launched into a long discourse on wave-particle duality, entanglement, and both the Copenhagen *and* the many-worlds interpretations.

"Stuff and nonsense!" replied the Cat. Being a cat, *and* a 19th-century one at that, he was of course a firm believer in Newtonian determinism and would have none of this new-fangled Germanic uncertainty. Just thinking about it, he said, made him quite giddy!

Alice then noticed a large steel box, with an open trap door at the top, lying on the ground behind the tree. "I see you're admiring my box," said the Cat. "It *is* a lovely box, isn't it? A gift from a human pet of mine. Although I'm not entirely certain what all that stuff inside is for."

Moving closer, Alice could see some sort of complicated apparatus in the box, with a Geiger counter and a broken glass vial. She thought it best though not to look any further, for fear of what else might be in there.

"But when I first saw you," asked the Siamese cat who now sat in the tree, "and you inquired about a 'Mr. Dodgson', didn't you have rather short dark hair?"

Alice thought this question very curious. Perturbed, she started to wonder if she might, likewise, be a Schroedinger Alice! " . . . and consist of a superposition of Tenniel-Alice and Liddell-Alice states!" Alice was certain she would not care for that at all, "for it would cause all sorts of confusion!"

These deep metaphysical waters were beginning to make poor Alice's head quite dizzy. “Things used to be so simple,” she sighed and decided it was time to say goodbye to the Schroedinger Cat. She had seen hatters before, so she thought to pay a visit to the March Hare, even if he *was *a postmodernist.

She thanked the Cat for the directions and started off down the path. But after a bit she wondered, "Did he say this goes to the March Hare's or to the Hatter's house?" and turned around to ask him. In the distance, she could just make out the Cat in his tree, but now rapidly disappearing and reappearing in a quite curious, flickering sort of fashion.

Alice remembered what her tutor had taught her about double-slit experiments and quantum interference, and decided not to disturb him further. As she continued her walk, she tried to recall what Derrida had written on the deconstruction of mid-19th-century Victorian literature.

"For it is almost certain to come up," she said to herself.