What Is Quantum Teleportation? by Dr. Stuart Rankin
Suppose Alice and Bojing work in laboratories in different cities (or planets) and Alice has a particle in an interesting quantum state. By a quantum state, we mean the state of a quantum system, such as an elementary particle, at a moment in time. If the particle were described instead by classical, not quantum, physics, its state would be described by precise values for its position and velocity. The quantum state of a quantum particle looks very different—you can imagine it as a complicated wave spread out over space, without a definite position in general. So what can Alice do, if she wants to give Bojing precise information about this state so that he can create it in his lab and study it too?
Unfortunately, she cannot simply measure the state of her particle without destroying the state (unless the state is a special kind of state called an eigenstate) and the measurement itself would provide incomplete information due to the uncertainty principle, which says that the more precisely you know one property of a particle—like its position—then the more uncertain you will be about another property, like its velocity. For example, an absolutely precise measurement of the particle’s position would have to destroy all information about its velocity, and indeed the original complicated wave would be collapsed down to just a thin spike over one point—the position reported by the measurement.
There is a solution for Alice; a way for her to communicate the exact state to Bojing. This is quantum teleportation.
Earlier, Alice sent Bojing one of a pair of particles in an “entangled” quantum state, while keeping the other of the pair herself. In an entangled state, each particle separately is not in a definite state—only the pair as a whole is in a definite state. A measurement on one member of the pair, however, obliges both particles to enter definite states—even if they are light-years apart! Also the result of the measurement on one particle determines the definite state of the other particle. Alice can make use of this by making a particular measurement jointly on her original particle and her particle from the entangled pair.
The result of this measurement she then sends to Bojing by ordinary means (e.g. e-mail or radio transmission). From this, Bojing can deduce both the definite state of the particle in his possession, and how to transform it into an exact replica of the state Alice wanted to send—but by making her measurement Alice is forced to destroy her initial state. Quantum information can be transferred, but not copied.
The end result is that Alice’s particle state has been teleported to Bojing! But only information—not matter—has been teleported; unfortunately for science fiction, this is not a way for people to travel. Instead, quantum teleportation is like faxing a letter—the information is printed on new paper at the receiving end, and the sender shreds the original letter.
Personally, I’d rather go by post!
Chapter Twenty
Annie and Leonia stood on either side of Cosmos’s doorway, with Leonia holding in both space-gloved hands the rope attached to Annie’s space suit. Under Annie’s feet lay the thick icy crust of one of Jupiter’s largest moons. When she looked down at the mottled and ridged icy sheet underneath them, she wondered if she had imagined the dark shapes moving beneath. She looked up. The very thin oxygen-light atmosphere of Europa meant that the dim rays of the distant Sun were diffused, to create a smoky glow across the sky. Through the smog, she could see Jupiter, the most magnificent of the planets in the Solar System.
Annie looked back to Leonia and pointed at Jupiter—and the two girls gasped. Tall, skinny Leonia seemed to sway a little in her suit, and Annie felt uneasy at having gotten her new friend mixed up in this adventure—she wished she had left Leonia out of it. The situation they were in was scary enough already without throwing a sudden and totally unexpected trip to one of Jupiter’s moons at even the super-competent Leonia. But as Annie floated gently away from the surface of Europa and only her space rope, held on to by Leonia, tethered her to something solid, she suddenly felt very glad to have her as backup. It wasn’t a moment to be operating alone.
“Stay right there,” Annie instructed Leonia, her voice going to Cosmos and bouncing back through the transmission device also fitted in Leonia’s space helmet. The space-suit technology they were using was certainly antique but it also seemed to be totally functional and very tightly stitched. It needed to be! In the freezing conditions of Europa, even a tiny leak would be the end of one or the other of them. She mustn’t, she knew, take a big step or she might float away across Europa and never make it back to the portal doorway.
“Why are the robots using heaters?” asked Leonia.
Annie turned to look at the robot army and their encampment. Now that she was actually on this side of the doorway, she could make out far more detail than when she had just been looking through the portal from the Earth side. Some of the robots were holding mechanical devices, which they seemed to be wielding around the edges of the very large gaping hole in the ice.
“I expect they’re trying to make the hole bigger,” said Annie. “If they didn’t apply heat, maybe it would freeze over again.”
By now, the robots had managed to get what looked like a net into the dark liquid. The girls watched as it sank beneath the ice. Around the edges of the robot-made hole, waves smacked at the hem of the circular incision in the ice. Annie floated a bit closer, letting out a little more rope. She had just seen something—or had she?—and she wanted to get another look. The glass in her space helmet wasn’t very clear—it was scratched and old—so she couldn’t tell if she had spotted something or whether it was a flaw in her space clothing.
“What was that?” It sounded like Leonia behind her had noticed the same thing.
“I don’t know,” said Annie. “It might be a bit of the machinery the robots are using.” But she still felt a sense of rising excitement. If she had just seen “something” in the dark liquid that lay under the surface of Europa, then she would be the first human being ever to have seen an alien! For years, there had been theories that alien life-forms could live under the icy crust of the moons of Jupiter and Saturn. Had they seen an alien? Did they look like dolphins in the oceans of the Earth? “I’ve got to get closer,” she said to Leonia. She edged away, rising gently from the surface in the low-gravity environment.
At that same moment, the shimmering white figure on the other side of the robot-made lake—like a ghost of a spaceman—became more defined. It was growing into its outline as it became more opaque.
“George,” called Annie. “George!” She waved. Perhaps if she caught his attention, he would fully arrive on Europa—perhaps she could summon him fully to the surface of this little moon by projecting her wish for George to be whole again onto the wavy humanoid shape on the other side of the dark, frothing pond.
It seemed to be working. Bit by bit, as though he was an illustration being colored in, George’s form fleshed itself out. It seemed agonizingly slow to Annie. She wanted him to arrive in solid form on Europa, so she would know he was in one piece. When all of him had arrived, Annie could start to work on getting all of him home. What scared her the most was the thought that part of George could get lost in space forever.
“C’mon,” she muttered to herself, willing George to make the transfer, whole and intact. “C’mon!” she said again to herself frantically. If she lost George, would she spend the whole of the rest of her life flying around space, looking for him like a lost soul? It was too horrible to contemplate.
But little by little, George was taking shape. First his arms seemed to become three-dimensional and solid. Then his legs, followed by his torso, and at last, his head and the round space helmet!
Annie gave a cry of joy. George had made it—and unlike some of the robots on Europa, who seemed to be missing limbs, it looked like all of him had arrived!
*
On the other side of the lake, in his space suit, George’s newly formed body plus head fully materialized on the icy ground. He felt himself
ping into his own body with a sickening lurch. Until he was sucked entirely into his own being, he had been lost in a world of strange dreams as particles of him transferred themselves across the Solar System. It was as though he had seen his own life played before his eyes like a film.
He had seen himself as a small baby, held in the arms of his proud parents with their hippy smocks and their wide young smiles. Then George had been a chubby toddler, playing with the family goat that had been kept tethered at the back of the wattle-and-daub hut where he had lived with his mom and dad. The hut had been part of a camp where families had lived in the same way as early Britons in the Iron Age, producing all their own food, heat, light, and clothing from what they could cultivate on the scrubby patches of land they had marked out for themselves.
But as a small child, George had fallen terribly ill and been rushed to a brilliantly lit hospital where his life had been saved by doctors using huge quantities of medicines and medical equipment. George saw his pale-faced mom and dad weeping by his bedside as they urged him to pull through. He saw his gran, the fierce but loyal Mabel, arriving at the hospital and shouting at his mom and dad for endangering their son’s life with the way they chose to live.
Mabel had finished by insisting that they move to a house—a proper house with electricity, running water, heating, and a roof! She had even bought it for them. In his dream George saw Mabel hand over the documents for the house. And he saw his parents give in and resign themselves to a life more ordinary, taking him from the hospital to the cozy little house that Mabel had given them.
But it wasn’t really a normal life. Despite moving into an ordinary suburban house in the town of Foxbridge, George’s mom and dad had continued to live their eco dream, using the back garden as their own little farm, attempting to generate their own electricity, making their own clothes, and trying to use as few resources taken from Planet Earth as they could. And one day George saw how the pig they kept in the back garden—another of Mabel’s thoughtful gifts to him—had run away, making a huge hole in the rickety fence that separated his back garden from the strange and overgrown world of next door. Following the hoofprints of Freddy the pig had led George through the jungle-like back garden of the deserted next door house right up to the back door where he met …
“George!” someone was shouting at him as though from the bottom of a lake. The voice was unclear and distorted, just like his vision, but still something seemed familiar to him. “George!” it came again. He didn’t know if it was part of his dream or whether he could really hear it. There was a strange ringing in his ears. When he tried to focus on anything, he just saw a swirl of darkness flecked with bright lights that flashed and whirred in front of his eyes.
But gradually the whirligig slowed down and the world stopped spinning. Through a haze, he could now make out a pale landscape with darker holes in it, and above, a grayish blue sky. Movement caught his attention—he could see darker dots, like ants, which seemed to be scurrying around the edges of the round holes in the grayish white surface.
And then he saw one figure more clearly than the rest. A white figure, waving at him from across a black expanse. “George!” he heard again, only this time he knew he wasn’t hearing this as sound. He was hearing it as a call from somewhere inside, as though his own self was calling him back into his body. He concentrated on the figure waving and realized it was coming toward him from the other side of the black hole. Was any of this real? He took a tiny heavy step forward, the space weights anchoring him to the surface, and then came to very suddenly.
And just in time! Once he looked around properly and saw where he had landed, George realized that one more step forward would have tipped him straight into the lake itself. Looking at the hostile liquid, which seemed somehow thicker and more viscous than water, George wondered what lay below. Was he imagining a mass of marine bodies seething just under the surface, twisting and turning in a bubbling soup of something indescribable? He couldn’t tell if he was still dreaming or whether he had seen this for real. But he could at least tell that on the other side of this lake-like expanse stood a small figure that he had seen in space before.
The figure waved at him, using both arms, floating away from the ground as it did so. Behind, in the distance, George could see another, tall figure in what looked like an enormous space suit, clutching onto a rope, standing in a faintly glowing doorway. “Annie!” said George to himself. Was it really her? Had his best friend come all this way to get him and take him home through the space doorway? Or was he hallucinating? Was this another strange dream? If the family goat from when he was a tiny kid turned up, he would know it was a dream. And if it didn’t, would that mean all this was real? How could he know for sure what was real and what was not?
The floating figure kept on waving. On either side of the figure and by the black lake, robots continued their work, unbothered, or so it seemed, by the presence of George and whoever else had made it to this weird world. George scuffled around to Annie’s side of the lake, the space weights heavy on his legs, without any of the robots seeming even to register his presence.
The robots all seemed to have different roles—some of them were using heat sources to make the lake larger. Others were holding onto an enormous net that seemed to have gotten stuck in the water. Some of the robots were reaching over the liquid to try to haul the net back onto the icy banks. But as they were struggling to pull it in, the effort and the icy bank meant robot after robot was toppling into the liquid, where they promptly sank without a trace.
While a whole cohort of robots vanished into the dark liquid, Annie and George both gave a huge sigh of relief as they met by the side of the lake. Annie was floating at head height by now, so George had to pull on her space boot to bring her back down to the surface. Hugging each other very briefly—and clumsily, since both were wearing space suits—George held on tightly to Annie and started walking her back toward the doorway. There, Leonia, the figure in the large old-fashioned space suit, waited for them on the other side. But before they could reach the doorway itself, they both felt, rather than heard, another presence behind them. They turned—and saw a shimmering apparition begin to take shape. The figure got rapidly clearer and clearer, until they saw that another person in a space suit was joining them, also arriving via quantum teleportation from Earth.
“Not so fast, George,” this new arrival said. Annie could hear the voice perfectly clearly too. “Have you forgotten?” it said. “Have you forgotten our deal?”
“I’ve done my part,” said George, hanging on to Annie for dear life. “I’ve traveled into space in the quantum teleportation device—and proved to you it can work with a living human being. So now you have to do your part of the deal and tell me where my family—and Annie’s mom—are.”
This was the first Annie had heard of any of this. George knew her hair would be standing on end—if that were possible—inside her space helmet.
“No, that’s not the full deal,” said the apparition regretfully. “If you’d read the small print—as I advised you to—you would have found that you signed up to go into space, collect an alien extraterrestrial being and bring it back to Earth for me. If you don’t meet those exact conditions, I am under no obligation to do anything at all for you.”
George ground his teeth. It was so typical of Alioth Merak to change the conditions of the deal once the action had already started. “That’s not what you said,” he persisted. “You only said I had to travel via the QT into space and then you would tell me where you are holding my family and Annie’s mom. That was all.”
“What!?” said Annie. “What do you mean, my mom! What’s she got to do with any of this? And who is that?”
“I can’t explain everything now,” said George, not letting go of his friend. They stood together, arms around each other, two small figures in their white space suits. “But we need to get out of here.”
“Cosmos,” said Annie. “And the portal—it’s just over t
here.” But she was still trying to understand what George had just told her. She stared at him. “You went through that teleport-thingy to save everyone!” she said. “George, how brave is that!”
George gripped her tighter, so happy to hear that he hadn’t let everyone down after all! But right now, they needed to get away from Alioth and his robots or it would all be in vain… .
They started to edge away, but more and more robots were starting to materialize as they traveled from Earth via the quantum teleportation device. Annie and George realized, to their horror, that in a very few minutes they could be overwhelmed. Annie looked behind her and saw Leonia was frantically gesticulating, but Annie couldn’t make out what she meant.
The next moment Annie knew what Leonia must have been saying. The portal doorway vanished entirely, taking Leonia with it—the door from Earth closed, leaving Annie and George alone on Europa with an evil robot army manifesting itself ever more distinctly by the second, and a crazed and very angry control freak, intent on revenge, just about to become fully fleshed in front of them.
Chapter Twenty-One
“So, my little friends,” cooed the rapidly solidifying form of Alioth Merak, formerly disguised as Rika Dur, head of Kosmodrome 2, now wearing a space suit and appearing via quantum teleportation on Europa. “We meet again. How charming this is!”
“It’s you!” said Annie in horror. The real voice was unmistakable. “Alioth Merak. How did you get here?”
“It’s been him all along,” said George grimly. “It was never Rika, at least not lately. I don’t know what he’s done with the real Rika. But he escaped from prison and he’s been impersonating her, using a 3-D printed face transplant, her clothes, a wig, and a computerized voice box.”
“Wow!” exclaimed Annie. She glared at Merak. “That’s why Rika turned against Dad when she came back from her vacation—it wasn’t Rika at all who got him sacked. It was you! You kidnapped Rika while she was on vacation and took over her role, didn’t you?”
George and the Blue Moon Page 19
