A puzzle for Eve

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“Bob,” said Eve in a tone that simultaneously conveyed both ultimatum and resignation, “Either you love me or you do not. There are only two possibilities: yes or no.”

Bob had objected to the framing of the question as a stark binary choice. “As a quantum physicist yourself,” Bob complained, “you of all people should understand that not only do such questions realistically require much finer gradations than a simple yes or no, but that whole realms of more nuanced and subtle possibilities are necessarily extinguished when one answers a question like that with just a ‘yes’ or ‘no.’”

Somewhat uncharacteristically, Eve found this line of reasoning both intellectually and emotionally unsatisfying. If it had been some abstract debate about logical possibilities, Eve might have played along, and might even have enjoyed the kind of back-and-forth pedantic discussion that she had found both charming and stimulating in her early dates with Bob. But this was neither abstract nor logical; it was about Eve and Bob, the not-at-all theoretical human beings, and how and whether they would continue a life together. Bob misread Eve’s face as amused introspection about the merits of his logical argument. Thinking that she was formulating either rebuttal or concession and looking forward to either intellectual possibility, Bob kissed Eve goodnight and went to bed.

The next morning, Eve watched from across the street as Bob and Alice, apparently smugly thinking they were being discreet, “happened” to arrive at the entrance to the hotel at nearly the same time. As they entered the hotel, Eve thought back to the moment she realized that this clandestine meeting was being arranged.

Bob and Eve had first met when they were both pursuing graduate degrees in quantum physics. Bob had been working on quantum multiverse theory; the idea that parallel words exist in alternate dimensions. He had some success in writing and gaining huge grants for gigantic machinery that was supposed to allow for some manner of interaction between universes, but few results had come from it. He was always going on about how there were a multitude of alternate universes in which whole populations of almost-doppelgangers lived almost identical lives diverging each time an alternate self had made a different decision, but even his own department head was starting to show some frustration regarding the lack of significant results or publications.

Eve had been intrigued by what she thought of as the more practical realm of quantum computing in cryptography. Quantum computing would open whole new worlds in both encryption and decryption, and in particular, would render some currently popular encryption techniques completely broken. She and Bob had discussed this at length and in detail. So it was particularly disappointing when, after Eve had described her latest successful quantum computing experiment in which she was able to trivially break ciphers based on the discrete logarithm problem to Bob, one morning she found a series of messages on their shared computer that were encrypted using that very cipher.

At first she ignored the encrypted messages, telling herself that they’d only be encrypted if Bob wanted to keep them secret, and so she should just let them be. As she drank her coffee and ate her English muffin, she then became annoyed that even after she’d described how terribly broken such encryption was in light of her latest research, that he’d apparently used it anyway. And finally, at least as she recalled it later, she wondered if it might be another of the kind of the mathematical puzzles that Bob had created for her amusement when they were first dating. Seizing on that last interpretation, she copied the messages to portable drive, picked up her favorite coffee cup (the one that Bob had given her that had Schrödinger’s wave equations printed on it) and went to her lab.

A few minutes with Eve’s experimental quantum computer was enough to easily decipher the encrypted messages that Bob had created. Instead of finding the kinds of messages she’d half expected (silly poems about Eve’s cat or maybe the recipe for Bob’s turkey tetrazzini), Eve trembled as she read the messages which were clearly not intended for her. “I am very much looking forward to meeting you, Alice.” “Meet me at the Exeter Hotel at 10 AM on Tuesday.”

Eve had not really thought through what she would do if she saw them. In some ways, she was still hoping that there was a flaw in her experimental computer or its algorithm, and that the messages she had read weren’t really the ones Bob had sent. However, as she waited across the street from the Exeter Hotel at a café, nervously sipping a latte and hoping that the floppy felt hat and dark sunglasses would prevent anyone from recognizing her, her heart fell as she saw Bob and the woman she guessed must have been Alice meet at the door of the Exeter and go inside together.

Eve didn’t really recall finishing her latte or crossing the street. She didn’t recall marching through the revolving door of the Exeter and making her way to the Exeter Lounge or even why she thought they might have been there. She only recalled standing beside the table where Bob and Alice were sitting.
“I’m glad you’re here,” said Alice.
“I told you she’d figure it out, even if she doesn’t really think much of my multiverse theories” said Bob.
Just as Eve was about to confront them both, she noticed a disconcerting familiarity about Alice. She had the same style and print dress as Eve wore, and the same floppy felt hat. When Alice removed her dark sunglasses and stood, extending a hand in greeting, it was like looking in a mirror.
“Eve,” said Bob, “I’d like to introduce you to, well, I guess, alternate you. Her name is Alice.”

About the Author: 
Ed is a research engineer and possibly a racecar driver in an alternate dimension.