Mike Omer - In the Darkness

Tatum frowned as he followed Jensen’s car. It was a testament to how badly things were between Zoe and him that she’d said she’d ride with the lieutenant. Tatum was terrible at holding a grudge. He knew some people did it with ease, practically turning it into a hobby. His aunt could recall what her frenemy had told her in eighth grade as easily as if she was recalling an event from the night before. But Tatum had to make a constant effort to do it, and it exhausted him.

Jensen parked the car in the university’s parking lot, and Tatum found a parking spot not far off. He joined Zoe and Jensen, and they all walked to the physics department. On their way, Jensen checked his messages and let out a curse. “The press found out about Maribel Howe’s phone call.”

“So fast?” Zoe asked.

“The girl’s mother probably called them straightaway.”

“She didn’t strike me as the type,” Zoe said.

Jensen didn’t seem to be listening. “Some of them are hinting at links between Howe and Medina. This is blowing up in our faces. I knew we should have given them more at the press conference.” His tone shifted, becoming accusatory.

Zoe pursed her lips. Tatum didn’t try to intervene. Arguing with the lieutenant was useless, he knew. The man was already trying to find someone to pin this on in case he was blamed.

Dr. Cobb’s office was on the third floor, and the door was open, but Jensen knocked on it anyway and said, “Knock, knock,” in a way that was perhaps meant to be endearing.

Tatum glanced into the room. Dr. Cobb was far from what Tatum had expected a physicist to look like. Cobb was a thin, black-haired woman wearing a buttoned white shirt and a pair of jeans. Her glasses were neither thick nor round but delicate and square. She had a bright-red lipstick on, which instantly made Tatum think of one of his early crushes in high school.

“Ah,” she said, her voice cool. “When you called, I thought I’d have some time to work before you showed up.” Her voice and demeanor hinted that Jensen might have exaggerated when he called her a friend.

“How are you, Helen?” Jensen asked, beaming. He entered the room and seemed about to hug her.

The doctor, clearly anticipating the move, stuck out her hand, and Jensen, after a moment of hesitation, shook it. Zoe and Tatum entered the room, and Tatum shut the door. He took one of the empty chairs in the room.

“Helen, these are Dr. Bentley and Agent Gray from the FBI,” Jensen said and then gestured at her, glancing at Tatum. “And this is Dr. Helen Cobb.”

Dr. Cobb nodded at them. “Nice to meet you. I understand you need my help with a . . . case?”

“There’s a killer who seems drawn to Schrodinger,” Tatum said. “We need a crash course about the cat experiment.”

Cobb sighed. “Well, it’s more of a thought experiment. Schrodinger never actually tormented any cats, as far as I know. The experiment is aimed to demonstrate a problem in the two-state quantum system. In quantum physics, we say a quantum can be in two different separate states at once. We call that superposition.”

Tatum could already feel his attention snagged by random thoughts. It was like being in school all over again, the drone of the teacher turning into a background noise as he fantasized about the girl who sat in front of him, about his afternoon plans, about frogs, about anything else, really.

“Schrodinger wanted to demonstrate that there is an inherent problem with superposition,” Cobb continued. “So he formed this thought experiment. You put a cat in a box. In that box there is a flask of acid connected to a device that has a Geiger counter and radioactive matter. Enough radioactive matter that in one hour, there is a fifty percent chance one of the atoms decays. If it decays, the acid kills the cat. If it doesn’t, the acid remains in the flask. With me so far?”

Tatum wasn’t sure. He really tried, but he was momentarily distracted by Cobb’s lips. How did her students ever manage to concentrate during class? He tried to pull his focus back together. A cat and some acid. Right.

“The matter in the device is in superposition. It decayed, but it also didn’t decay. It’s in two states at once. The cat was either exposed to the acid, or he wasn’t. Which means he’s both dead and alive at the same time. He’s in superposition.”

“But he is either dead or alive. He can’t be both.” Zoe sounded irritated. Tatum wondered why she found this so offensive. Perhaps she was averse to cruelty against imaginary cats.

“Well, the thought experiment states he’s in superposition, because he’s in a closed, unobserved device that is in superposition. So the cat and the device are in the same state.”

“When you say unobserved, what does that mean?” Zoe asked.

“Superposition can only exist if the matter isn’t measured. Once it’s measured, it can’t be in several states at once.”

“What if we looked at the cat via a video?”

“Then it wouldn’t be unobserved. So the cat wouldn’t be in superposition.”

“What if we observed the cat through a video, but then the feed was terminated?” Tatum asked, suddenly tense. “And then the experiment carried on without anyone observing it?”

Cobb hesitated. “After a while, the cat would be in superposition. He would be both alive and dead.”

Was that why the killer had cut the feed, leaving them in uncertainty? Was it part of the experiment? Tatum clenched his jaw. Would he do other experiments?

“What if there was no acid in the box?” Zoe asked, rummaging in her handbag.

“Then the cat would presumably stay alive.” Cobb scrunched her eyebrows.

“But he could die from lack of air.” Zoe pulled out a copy of the case file and flipped through it, a pen in hand. She made a small notation on one of the pages.

“Yeah, but that’s not a consequence of a quantum device, so he wouldn’t be in superposition. He would be either alive or dead, not both.”

“But we don’t know which—doesn’t it mean he’s in superposition?”

“No.” Cobb shrugged. “My husband is currently at home. He’s either eating or showering or reading or whatever, and I have no idea which. That doesn’t mean he’s in superposition. Because his state isn’t connected to a particle. And obviously, he isn’t a particle. He’s my husband. That’s also part of the problem with the experiment. It has been proved a cat can’t be in superposition.”

“Why not?”

“Because he’s too big. Big things can’t be in superposition. It doesn’t matter if the cat explodes or not—he would never be in superposition, because he’s too big.”

“Explodes?” Zoe asked. “You said he’s killed by acid.”

“Well, in Einstein’s version, he’d explode. Einstein’s experiment had a barrel of explosives. It really doesn’t matter. The point is, it’s something that kills the cat.”

Apparently physicists liked to theoretically abuse cats in any number of ways. Perhaps Marvin would find that notion appealing, considering his long feud with Freckle. “So humans can’t be in superposition either, right?” he asked.

“Of course not. Humans are bigger than cats.”

“Dr. Cobb,” Zoe said. “Was the experiment ever performed?”

“God, I hope not.” Cobb shuddered. “What would be the point? The entire thing is intended to demonstrate a paradox. You don’t actually need to trap a cat in a death machine to do it.”

Unless the purpose of the experiment was different and wasn’t about science at all.

Andrea missed Boston.

That was the main thing she realized as she ran on the gym’s treadmill. She missed jogging through Boston Common. Right now, the trees would be turning yellow, red, and pink, and running through that explosion of color would be—