The Place Where the Crystal Was Still

The crystal did not look like a place where anything could get lost.

It was smaller than Soren's thumbnail, pale and polished, clamped under a glass cover in the middle of Dr. Imani's workbench. Gold teeth lined its edges in combs so fine they blurred unless he leaned close. Wires ran from the combs to a silver box. The box ran to a screen. The screen was supposed to show a red pulse crossing from one side of the crystal to the other.

Instead, the red line lay flat.

Dr. Imani made a sound like she had bitten a lemon. She tapped the screen with one knuckle. The red line remained flat.

"Of course," she said. "Of course it dies today. The review team arrives in twenty minutes. Soren, don't breathe on anything expensive."

Soren took one careful step backward and wrote, Red line flat. He used a pencil because pencils did not run out of battery and because crossing things out helped him think. The lab badge on his shirt still said Visitor, although Dr. Imani had crossed out Visitor and written Temporary Helpful Person underneath.

The chip was for a spacecraft panel that had to move heat away from delicate instruments without pumps, fans, or anything with a wheel. Dr. Imani had explained this while looking for a missing screwdriver and drinking cold coffee.

"Sound and heat both ride through solids as vibrations," she had said. "In a crystal, the atoms are arranged in a pattern. They shake in allowed ways. We call the little packets phonons. If we can steer them, we can steer heat. Maybe. If the universe behaves and the grant committee does not ask silly questions."

Soren had written, heat can ride a shake.

Now the universe was not behaving.

Dr. Imani pulled one wire, replaced it, frowned harder, and checked her wrist display. "Dead receiver," she said. "Or cracked wafer. Or both. I should have built two. I always say I will build two, and then I believe myself, which is the first mistake."

Soren looked at the screen. The flat red line had tiny teeth on it. Not noise exactly. More like a fence very far away.

"Can I ask it one thing at a time?" he asked.

"Ask quickly," said Dr. Imani. She was already opening a drawer with her elbow.

Soren did not touch the crystal. He touched the control tablet beside it. The tablet had a diagram, left comb, right comb, center receiver, edge receivers. Two green buttons said launch. One for each comb.

He turned off the right comb.

The screen jumped.

A red pulse rose from the left, neat as a heartbeat, and arrived at the center receiver.

Dr. Imani froze with a screwdriver between her teeth.

Soren wrote, left only works.

He turned the right comb on and the left comb off.

Another pulse rose and crossed the other way. The red line at the center receiver jumped again.

He wrote, right only works.

He turned both on.

Flat.

The screwdriver fell out of Dr. Imani's mouth and landed on the mat.

"That is rude," she said.

Soren turned both off. Then left. Then right. Then both. He did it three more times, because one time was a trick and two times could be an accident, but six times was trying to tell you something.

Left worked. Right worked. Together, nothing arrived in the middle.

Dr. Imani leaned over his shoulder. Her hair was escaping its clip in black loops. "That should not be possible."

Soren pointed at the two small blue traces from the edge receivers. "They get bigger when both are on."

"Yes, but the middle gets nothing."

"Not nothing everywhere," Soren said.

He picked up his pencil and drew the crystal as a rectangle. Left wave. Right wave. Center dot. Then he drew humps meeting humps, which made a taller hump. Under that he drew a hump meeting a dip. They made a line.

Dr. Imani looked from the drawing to the chip. "Interference," she said, but she said it like someone naming a culprit, not giving an answer. "No. The combs share the same clock. They launch together."

Soren looked at the chip through the magnifier. Between the left comb and the center receiver, the crystal was plain. Between the right comb and the center receiver, there was a tiny field of holes drilled in rows. Not random holes. A pattern of holes, like a city for something smaller than dust.

"This side has a maze," he said.

"A phononic crystal section," Dr. Imani said. "It slows certain vibrations. Opens band gaps. Steers the acoustic mode. It is the point of the demo."

Soren watched the flat red line. "Then they don't arrive together."

"They are launched together."

"That's not the same."

Dr. Imani opened her mouth, shut it, and looked at the clock. "I have to call downstairs before the reviewers get lost and judge us for our elevator. Do not change the voltage. Do not increase the power. Do not discover fire."

She hurried into the hall with her wrist display raised.

Soren sat very still. The lab hummed around him. Air cleaner. Cooling pump. Someone laughing two rooms away. Under all of it, the silver box clicked once each time it launched the waves into the crystal.

Click. Flat line.

Click. Flat line.

The combs were not speakers, not exactly. They squeezed the crystal electrically, and the crystal answered by shivering. The shiver ran along the surface faster than sound in air, slower than light, carrying energy through the ordered atoms. On the screen it was a red pulse. In the math it could be counted in phonons. In Soren's pencil drawing, it was a hump and a dip meeting in the wrong place.

The tablet had a slider labeled phase. It was set to zero.

Soren did not move it yet.

He turned on a side camera. A microscope view appeared beside the red trace. The crystal surface looked empty until he adjusted the light. Then he saw them, tiny silver specks Dr. Imani had sprinkled on the glass cover to show where the surface was shaking hardest. They quivered when one comb launched. With both combs on, the specks near the edges trembled, but the specks over the center rested as if the crystal below them had gone asleep.

He touched the phase slider and moved it one small mark.

Click.

The red line twitched.

He moved it another mark.

Click.

The twitch grew teeth.

Soren's pencil rolled off the bench. He let it fall.

He moved the slider slowly, mark by mark, while the silver specks began to crawl into pale lines. The red pulse rose out of the flatness. First a bump. Then a hill. Then a sharp bright peak that made the screen rescale itself.

Dr. Imani came back in saying, "They took the stairs, which means they are already suspicious of civilization," and stopped in the doorway.

The center receiver pulsed red. The edge receivers pulsed blue. The thermal camera, which had been a square of dull colors, showed a thin warm path crossing the chip.

"Soren," Dr. Imani said, very quietly, "what did you change?"

"When the maze makes one side late, the other side has to start late too," he said. "Or early. Depending which way you count."

Dr. Imani came closer. She did not touch the controls. "You phase matched them."

Soren picked up his pencil from the floor and put it beside the tablet. His hands were buzzing, but not from the bench.

Footsteps sounded in the hall. Adult footsteps, several pairs, all trying to be calm and important.

Dr. Imani looked at the working screen, then at Soren's rectangle full of humps and dips. "The review team is about to ask for the simple version."

"Don't give them that," Soren said.

She smiled at him, quick and crooked. "Absolutely not."

The reviewers entered with clean shoes and bright badges. Dr. Imani began talking too fast about heat paths and acoustic modes and spacecraft panels that could cool themselves by steering vibrations through crystals. Soren stood to the side, where Temporary Helpful Persons belonged, but the microscope screen was still open.

One reviewer asked, "Can you turn the heat path off without turning the device off?"

Dr. Imani glanced at Soren.

Soren moved the phase slider back to where it had begun.

The red pulse disappeared. The warm line faded. The silver specks over the center stopped moving.

No one spoke for a second.

The reviewer leaned closer. "You canceled the vibration there."

Soren moved the slider forward again. The pulse returned.

The reviewer laughed once, not because anything was funny. "Like making darkness with light."

"With a crystal," Soren said.

Dr. Imani's crooked smile got wider.

After the review team finished asking questions, they did not leave right away. They stayed around the bench, watching the red line appear and vanish as Soren slid the phase back and forth. Dr. Imani let him do it. She even moved her coffee away from his elbow.

Then Soren noticed a third green button on the tablet. It belonged to a comb at the top edge of the chip, one he had thought was only a spare. Its gold teeth pointed down toward the others.

"What happens with three?" he asked.

Dr. Imani looked at the button. "That part is not in the demonstration."

The reviewers looked at the button too.

Soren waited.

Dr. Imani put both hands in the pockets of her lab coat. "Do not increase the power," she said.

Soren turned on the third comb.

On the monitor, the silver specks slid away from the center of the crystal and gathered in two bright lines. Between them, one square stayed empty. Soren set the pencil down and placed his fingertip on the glass above it.