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02 -- Lasing with a Chain Gang

Alice couldn’t wait to get back to Quantumland. She’d spent the better part of the past week helping Mother host three teas and two garden parties in honor of her newly engaged sister Mary. Alice thought planning a wedding was pretty boring compared to scoping out a strange, cold world filled with odd creatures like talking atoms (the tiniest particles of matter).

At last, she was able to tiptoe across the back lawn through the gardens. She spied the White Rabbit peering out of his hole, looking askance at the crowd of women and girls congregated on the lawn. As soon as the White Rabbit spied her, though, he hurried back down to Quantumland, with Alice in hot pursuit.

“Wait, wait,” she cried, watching him disappear through a door too small for her to follow. Frustrated, she sat down next to a table with a strange-looking device on it labeled Superradiant Laser. “Mmm,” wondered Alice. “I wonder if this device really emits a giant wave of light. Perhaps, I should take a look inside and see.”

Spying the bottle labeled Drink Me, she took a long, slow drink and hopped up into the laser just before she got too small to make the leap. “Wow,” she thought. “It’s really dark in here.” As her eyes adjusted, she saw a long chain of identical atoms. They were just hanging out and resting. She approached the atom closest to her and introduced herself.

“I’m Alice, and I’m wondering why you’re all just sitting here,” she said. “Aren’t lasers supposed to lase? You know, emit a light wave?”

The atom looked lazily at her. “I’m a rubidium atom, but you can call me Ruby,” the atom said at last. “All my friends here are named Ruby, too. That’ll be your name too when “Boss” Red Photon shows up.”

Alice wasn’t sure she liked the name Ruby, but she didn’t have a lot of time to think about it before a particle of bright red light blazed through the laser, cracking a whip and shouting, “All right you Rubies, time to rock and roll!” Clearly Boss Red Photon had arrived.

“Ruby, are you and your friends part of some kind of chain gang?” Alice whispered.

“Yes, we are, and so are you,” Ruby answered as she began to vibrate in unison with all the other rubidium atoms. “You’d better get into your excited state, pronto.” Alice decided to do the twist since it involved gyrations similar to what the Rubies were doing.

Just as she was finding her rhythm, Boss Photon shouted, “Relax!” The Rubies all emitted photons at the same time, creating one big wave of light that carried away all their excess energy. The Rubies became relaxed and calm. However, Alice wasn’t sure whether she had emitted a photon of light since she was actually a little girl and not a rubidium atom.

Spying her friend Ruby, Alice asked her to explain the quantum story behind what had just happened.

“There’s nothing quantum about how this laser works,” she said. “It’s all classical physics. The same thing happens when two metronomes start ticking together when placed on the same piano, or when two grandfather clocks sitting on the same floor keep the same exact time because their pendulums swing in sync. Getting all the Rubies (and an Alice) to lase is pretty much the same process that gets an audience clapping in unison after a popular concert, fireflies blinking at once, or crickets singing together in one loud voice.”

Alice was sad. She’d come back to Quantumland to learn more about how the quantum world worked. And now, superradiant lasing didn’t seem to be any more complicated that a swarm of fireflies blinking on and off in lock step!

“Ruby,” she said. “Is there any quantum excitement going on down here?”

“Maybe so,” Ruby answered, to Alice’s surprise and delight. “Doc Walrus thinks that if someone sets up another superradiant laser on the table really close to us, the atoms in both lasers might merge into a brand new and bigger laser!

“Doc Caterpillar says the same thing would work with two strontium atomic pocket watches, too. And, if there’s one thing I know since I’m an atom myself, it’s that when you start trying merge hundreds of thousands of us, things can get pretty wild and crazy before we all get synchronized again.”

Just then, Alice heard a big commotion just outside the laser. She peeked out and discovered that Doc Walrus’ sidekick Doc Caterpillar was setting up a brand new superradiant laser on the table, just nanometers away from her head. “Now what?” she wondered as Boss Photon zoomed back through yelling at all the Rubies to get excited.

Alice started dancing the twist, but immediately got distracted. All she could think about was Hamlet’s soliloquy: “To be or not to be, that is the question.” On the one hand, it seemed like an OK thing to do to join up with other Rubies to make a bigger laser. On the other, it seemed like it would be better if things just stayed the same. Two lasers might be better than one and would certainly be less crowded. “I just don’t know what to do!” Alice cried in exasperation.

Alice got so wrapped up in trying to decide what to do, she forgot all about doing the twist. But, she couldn’t relax either. All her Ruby friends were struggling with the decision whether to merge or not, too. Their synchronization completely disappeared, leaving the atoms in the dark with so much quantum confusion, it was hard to think at all, much less make such an important decision!

Boss Photon tried his best to get the Rubies and Alice back working together on the chain gang, but to no avail. The ensembles of atoms in each laser were trapped in a quantum identity crisis, with each atom debating whether to stay put or join forces to make an even bigger and more powerful laser. The amount of uncertainty inside the two smaller lasers created so much quantum confusion both lasers stopped working—for the nanoblink of an eye.

At last, the Rubies (with Alice’s help) made a collective decision to merge. A large superradiant laser took shape on the table as the two smaller lasers disappeared, leaving nary a smile behind. Boss Photon, breathing a sign of relief, blazed back into the new laser to whip the new ensemble of Rubies into a bigger, more powerful chain gang. Alice quickly hopped out of the new laser. She jumped off the table as the shrinking potion began to wear off. Turning toward the new big laser on the table, she could see the new laser was sending out a bigger and brighter wave of red light!

“Whew!” Alice exclaimed, happy that things had quieted down and her Ruby friends were back at work. “That was some quantum identity crisis!”

Alice raced back up the rabbit hole, arriving just in time to say goodbye to the last of her sister’s guests. She enjoyed the moment of genteel sociability. It was a nice change from working on a chain gang inside a superradiant laser.

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