MP Ch145: Schrödinger and decoherence

[02/28, 11:45, Shengzhou City, Dongli Technology University]

The class bell rang, and Lian Jingyuan announced the end of the class. He did not hurry to pack his books because the lovely and studious students still wanted to surround him with questions, most of whom were female students. Each time, they would extend the conversation into topics unrelated to the textbook.

“Teacher Lian, I heard you got a pet last time; is it a cat or a dog?”

“A cat, I was helping a friend take care of it, but it has already been returned.”

“What a pity! I really want to see what Teacher Lian’s little cutie looks like,” a female student blinked. “Does Teacher Lian still want to raise a cat? My cat just had a litter of kittens; I can give you one~”

“No, thanks. I’ve been too busy lately and don’t have time to take care of it,” Lian Jingyuan pushed up his glasses. “Thank you for your kindness; it’s getting late, so everyone should disperse.”

Once he walked out of the teaching building, Lian Jingyuan finally let out a sigh of relief. Looking at his wrist, he realized it was getting late, and he hurried back to his office.

“Ding,” the elevator stopped on the fifth floor of the administration building. Lian Jingyuan quickly exited the elevator, and he encountered several colleagues who greeted him. Those who were closer stopped him and whispered, “Jingyuan, you haven’t offended anyone, have you?”

“No. What’s wrong?”

“There’s a man standing at your office door; he’s been there for a long time, wearing a hat and a mask, looking very suspicious. Should we call security?”

It seemed the person had arrived. Lian Jingyuan smiled gently, “No need, he’s my friend.”

His office was at the very end of the corridor. After turning the corner, he saw a tall figure standing against the wall, rigid and unmoving, radiating an aura of “keep your distance.” No wonder he was mistaken.

Hearing the footsteps, the person turned his head to look. Upon seeing Lian Jingyuan, he lowered his mask, revealing a finely featured and handsome face.

“What time did you come? I heard you’ve been waiting for a long time.” Lian Jingyuan held a book in one hand and took out his keys with the other to open the door. “I didn’t expect to see you so soon, Yi Shi.”

“Eleven o’clock; it’s not too long of a wait,” Yi Shi said. He had arrived on the high-speed train quite early, and being unfamiliar with Shengzhou, he had no desire to appreciate the strange scenery, so he simply came to the school to wait for Lian Jingyuan to finish class.

Opening the office door, Lian Jingyuan welcomed him in and asked, “Have you eaten? Do you want to order takeout?”

Yi Shi shook his head; he wasn’t hungry and didn’t want to delay Lian Jingyuan for too long.

Lian Jingyuan didn’t mind; he had no classes this afternoon; otherwise, he wouldn’t have agreed to meet. He had received the call in the middle of the night yesterday. From Yi Shi’s tone, he could tell that he was very distressed and helpless, and Lian Jingyuan guessed it was related to unknown science, which sparked his intense interest to meet and talk.

Yi Shi closed the door and found a chair to sit down. Lian Jingyuan noticed he was using his right hand to grab the chair and asked, “How’s your injury?”

“Guess.”

“It seems to be recovering quite well.”

Yi Shi rolled up his sleeve. Other than the ghastly old scars, there were no signs of gunshot wounds. Lian Jingyuan was surprised and pulled his arm to observe closely. Their eyes met, and that gaze was filled with a strange smile, the coldness in the depths melting away; it was him, but also not him…

“Don’t doubt, I’m Yi Shi.” He stopped playing games and spoke frankly. “The Yi Shi you met before is the present Yi Shi; I’m the future version of him.”

“Oh… I see.” This concept did not confuse Lian Jingyuan, a physics scholar, but he was still a little surprised and couldn’t help but joke, “How lucky! I get to meet two versions of you. Looks like my paper has a chance now.”

The atmosphere instantly became lighter. Yi Shi inadvertently looked down and spotted a few feathers sticking out from under the desk. He reached down to pick them up; it was a toy mouse with a feather at the tail.

“Do you have pets?” Yi Shi handed the little toy over. Lian Jingyuan took it, muttering, “… How strange, it shouldn’t be here.”

Yi Shi pointed to the desk; it was right underneath, and there was no dust on it, clearly having fallen there not long ago.

Lian Jingyuan frowned, unable to recall when he had brought the cat toy to the office and who else could have done it if it wasn’t him, especially since the cat named Stephen had long since… returned?

He put the toy mouse in a drawer, clasping his hands together over his chest, “Forget it; it’s not a big deal. Let’s get started.”

Yi Shi took out a few folded A4 papers from his pocket and handed them over. Lian Jingyuan had a premonition that the content inside was closely related to the parallel world. The last time they met, they were still unfamiliar with each other; Yi Shi had only revealed some superficial information. This time, he was prepared to be open and straightforward.

The other party handed over a trust and responsibility like this, and Lian Jingyuan became more serious. He opened the A4 papers one by one, which included two sheets of filled-out date tables, from October 1 to March 1; a list of names with numbers in parentheses that seemed to represent ages; and a complex deduction diagram.

All the text on the paper was reversed. Lian Jingyuan turned on the all-in-one machine, scanned the A4 sheets into a document, then adjusted them in Photoshop, and reprinted them with the text in the correct orientation.

“This looks more convenient, thanks to technology.” Lian Jingyuan first picked up the table. “The time periods listed here represent the complete duration of the experience? Do Y and L refer to you and your friend?”

Yi Shi nodded, pointing to a name in the relationship chart: “His name is Lin Heyu.”

“Hmm. Wait a moment; don’t give me hints yet. Let me finish and guess.”

In less than three minutes, Lian Jingyuan said, “The dates of the intersection points are quite distinctive, like ‘11.21’ and ‘12.11’, ‘12.10’ and ‘1.21’, etc. I remember you mentioned last time that your worlds are reversed, right?”

“Yeah, the flow of time is opposite. We call the dates with corresponding points ‘mapping points.’ Time outside the mapping points flows normally.”

“What about the dates without mapping points? How did you meet?”

Yi Shi thought carefully: “Most of the time, it’s through the passage of time, just like the café where we first met. There have been a few crossings in the water, as well as during the case.” He frowned habitually. “Actually, we haven’t summarized any fixed rules. Sometimes crossings happen unexpectedly, and sometimes it’s difficult to meet.”

Lian Jingyuan circled a few dates with his pen, categorizing them according to Yi Shi’s words. He stroked his chin: “In my view, mapping points are a fixed rule for the convergence of parallel worlds. In the absence of mapping points, all crossings depend on the contact between you.”

“We… do we include all of us?” Yi Shi patiently recalled: the fountain, Cheng’an Mountain, including the small stone they saw that day. It seemed that the merging of parallel worlds occurred among the four of them. He and Lin Heyu always thought that the crossings in the cases were simpler, but that was because their contact was more frequent in those situations.

“Of course, this is just my speculation based on this table. There may be other factors, after all, I can’t verify it personally.” Lian Jingyuan pushed up his glasses. “But at least this kind of quantitative change is fixed; the particle evolution cycle occurs between you, which is why it affects the so-called life trajectory.”

Hearing this, Yi Shi felt he had found the right person.

Next, Lian Jingyuan picked up the list of names, and Yi Shi reminded him, “The original arrangement wasn’t like this; this is the result of my rearranging after mixing it up.”

“It’s obvious that the age difference between the corresponding two names is twenty years; you can immediately see the direction of the flow of time. If the original world was like this, you wouldn’t have come to find me. This is the result you hoped for, right? You should keep it well; it might help restore things to normal.”

Yi Shi was silent for a moment and then spoke solemnly: “That’s the reason I came to find you. The ‘normal’ that Lin Heyu and I are pursuing is actually the outcome we least desire. We have already discovered the key points of the case, but she is someone very important in our lives. If we go back to normal, she will not exist.”

In another deduction diagram, a name frequently appeared—Lin Zhizhi. Lian Jingyuan speculated that she had a familial relationship with Lin Heyu, but then he saw her in another identity during childhood, as Gardenia, who was Yi Shi’s younger sister. Strangely, twenty years later, she adopted Yi Shi, becoming his adoptive mother.

Such a complex identity relationship was astonishing; the layering of multiple identities was somewhat like the protagonist in Predestination. However, based on the physics paradox, that could only exist in movies, as an artistic setting. In Yi Shi’s case, the paradox rules did not cease to function, but it was due to the vast age difference of the same entity that allowed coexistence. However, he had also said that Lin Heyu encountered his parallel self and would still be forced to evade, having no chance of “killing himself.”

As for whether one could kill their younger self, Lian Jingyuan believed that parallel universes would have their own set of rules to prevent such paradoxes from occurring.

“Zhizhi is very important to us, but Lin Heyu and I also don’t want to keep looping like this, so I came to you to find a way for all three of us to exist.”

Yi Shi’s tone was exceptionally firm. Lian Jingyuan tapped his chin with his index finger: “I think you’ve probably seen many related types of movies. The inability to achieve a perfect choice isn’t intentional, but based on certain theoretical foundations. In a multiverse, every decision creates a new parallel universe, layering probabilities into the thousands. It’s nearly impossible to find a perfect life among them; at most, you can only approach it, but it’s not absolute.”

“I’m not pursuing absolute perfection; I only want a relatively better outcome than now. Zhizhi, I, and Lin Heyu can all exist fully without having to go through the loop again.”

If that were truly the case, it would count as a perfect happy ending. Lian Jingyuan twirled the pen in his hand repeatedly. Yi Shi and Lin Heyu wouldn’t give up on Lin Zhizhi, nor would they give up on each other. They currently dared not attempt to revert to normal, fearing that without the opportunity to restart, they would lose the most important person.

“Schrödinger’s cat was proposed to satirize the ‘superposition state’ in quantum mechanics. In quantum mechanics, when there’s no external observation, the quantum is in a contradictory ‘superposition state,’ meaning the cat exists in a state of being both alive and dead; any form of observation will cause the quantum to collapse from the superposition state into a definite state, that is, when the box is opened, determining whether the cat is alive or dead in one of those states. However, in life, there is no ‘cat that is both dead and alive’; the one who decides the cat’s state is the ‘person’ who opens the box.”

“Around this experiment, many subsequent physical questions and philosophical debates were extended, and the multiverse is one of them.” Lian Jingyuan took out two pens. “The cat locked in the box exists in two parallel universes, one where the cat is alive and the other where the cat is dead. While in the box, they are entangled together, but when we open the box, the two universes split apart. We cannot determine which universe we see in advance, but outside our observable universe, the other universe certainly exists.”

He stood up, took a book titled Quantum Universe from the shelf, and placed it in front of Yi Shi: “The overlap of two parallel universes generates quantum coherence. It’s difficult to maintain this for a long time because once it encounters external observations, it loses coherence, which is called ‘decoherence.’ This theory was mentioned in Coherence, oh right, its literal translation is ‘coherence.’ I heard colleagues complain during the last physics conference that the Chinese title of this movie is too literary.”

“Comets serve as an external force that generates coherence, intertwining multiple universes together. After the comet leaves, coherence dissipates, and the multiverse returns to normal, no longer producing intersections. In the world you’ve experienced, the key point of decoherence lies with Lin Zhizhi. Although her state resembles Schrödinger’s cat, according to this chart, there are indeed two of her in this world, right?”

Yi Shi nodded. The string of theories was somewhat confusing, and Lian Jingyuan circled the names Lin Zhizhi and Gardenia on the paper. “They are the same individual, but currently not the same person. Why not try letting her be the one to open the box?”

“Let Zhizhi… give it a try?”

“Rather than you both struggling for so long, why not let her decide her own fate? I believe many people have had this experience: always being arranged by their parents without any opportunity to choose for themselves. They all hope their parents will listen to their voices, and I think Lin Zhizhi feels the same way. Compared to you, she has more right to know all of this and is more suitable to make her own choices.”

“…I’m afraid,” Yi Shi lowered his head, running his fingers through his hair. “If Zhizhi knew, she would definitely feel guilty and scared. What’s worse is, what if she chooses to sacrifice herself?”

“Isn’t your current choice a form of self-sacrifice? In my opinion, you two are the ones making the greatest sacrifice. You always say you want to exist together, but if you really can’t have both, you’d still prefer to use your lives to ensure Lin Zhizhi survives, right?” Lian Jingyuan patted Yi Shi’s shoulder. “I’m not saying this without understanding; I just want to tell you that some choices aren’t selfish, and you don’t need to shoulder all the blame.”

“Moreover, it doesn’t necessarily mean true death. Think about what I just said regarding Schrödinger’s cat. When you observe the cat’s dead state, you’re only seeing the parallel universe where the cat is dead. There’s another parallel universe where the cat is alive. However, after decoherence, the two worlds can no longer intersect, and you won’t have the opportunity to see each other.” Lian Jingyuan rubbed his temples and sighed softly. “Still, the point is that nothing can be absolutely perfect; there’s only the attempt to make it as close to perfection as possible.”

Yi Shi fell into deep thought, and Lian Jingyuan didn’t disturb him, picking up the book he hadn’t finished reading earlier. Fortunately, he didn’t have classes in the afternoon and could accompany Yi Shi through this. However, Yi Shi probably couldn’t wait much longer; he and Lin Heyu were already in a countdown, and every choice was pressing.

Finally, Yi Shi stood up. “Thank you for today; I should head back.”

“Don’t mention it. If our conversation today can help you, that would be my honor.”

Yi Shi nodded, put on his mask, and as he reached the door, he turned back. “Last time I promised to treat you to a meal, but time was too tight. If I’m still in this world after decoherence, I will definitely make up for this meal I owe you.”

Lian Jingyuan smiled and waved at him. “I look forward to our next meeting.”

———

[02/28, 17:46, Nanyi City, Changlong Garden]

“…That’s roughly it. Lian Jingyuan suggested letting Zhizhi be the one to open the box.”

Yi Shi twisted open a bottle of mineral water. Having spoken so much at once, his throat felt parched. Lin Heyu’s reaction mirrored his, immediately rejecting the idea. “No, we can’t let Zhizhi know. She’s kind and fragile, and she wouldn’t want to put us in a difficult position.”

“I understand. I used to think like you, trying to avoid involving her as much as possible, but she’s already in the midst of it.” Yi Shi shook his head weakly. “…In my world, Zhizhi has already discovered your existence and has begun to suspect Sheng Guoning. I want to change the existing pattern, to find a breakthrough point, so I dragged her into this too.”

He kept his head down, mentally preparing himself, not arguing no matter how Lin Heyu scolded him. Lin Heyu had always treated Lin Zhizhi as a younger sister; after their parents passed away, she was his only family. In his mind, a sister should only enjoy life, while he and his future partner should bear all responsibilities and burdens.

Let him scold away. Yi Shi closed his eyes. Since it was already done, it was better to accept it calmly rather than feel regretful.

To his surprise, he was met with a warm and comforting hand. Lin Heyu rubbed his dark hair, offering reassurance.

“Since it’s already done, don’t think too much about it. Try to look at it from a different perspective; it might just be a part of the predetermined facts.”

Yi Shi opened his eyes. “…You really won’t blame me?”

“Your relationship with Zhizhi is closer than mine; I have no reason to doubt that you would harm her.” Lin Heyu pinched his cheek. “Before Sheng Guoning self-destructed, you had no idea what this key point was. You just guessed that it had something to do with Zhizhi. If it were me, I would also take a risk in a stagnant situation.”

Yi Shi felt a bit choked up and hugged Lin Heyu tightly, trying to absorb his warmth.

He loved Lin Heyu the most. Only Lin Heyu deserved all his feelings.

The two embraced tenderly, and after a brief moment of closeness, they had to consider the choices before them. Neither of them was very in favor of letting Lin Zhizhi make a choice. Sheng Guoning certainly wouldn’t agree; he was more afraid than anyone of losing Zhizhi. This suggestion from Sheng Guoning seemed to have been shelved for the time being.

Now, Muli City was bustling. In the present time, Lin Heyu, Yi Shi, the small stone, Gardenia, Lin Zhizhi, Sheng Guoning, Zhao Chenghu, and his underlings all felt like a chaotic stew. They decided not to interfere, at least until Lin Zhizhi’s existence was confirmed.

Speaking of that Volkswagen car, Lin Heyu smiled. “Can you guess why it can’t be found? Don’t overthink it; guess simply.”

“Stolen plates?” Yi Shi frowned. “But we saw it on the riverbank that day; I took pictures without any replacements.”

“That’s another ridiculous and bizarre point. Remember what Xu Shang mentioned in his testimony about the explosives?”

Yi Shi nodded; Xu Shang had mentioned hearing them argue about the color of the wires. Could it be…? He widened his eyes. “Are Tu Laogui and Pang Daozi at odds to that extent?”

“Yes, the car belongs to Lin Erde. Zhao Chenghu took the ransom money directly to get the plates, but he never used them. A few days later, Tu Laogui found out and, feeling dissatisfied, had him switch them back.”

“……” Yi Shi felt that familiar sense of speechlessness, like when he heard his little brother had messed something up, and decided to change the subject. “Should we go pick up Xiao Shitou tomorrow?”

“Yeah, let’s go. We also need to rescue the hostages trapped on Peacock Head Mountain. The predetermined fact of a good outcome needs to be followed.”

“What about you?”

“Me?” Lin Heyu’s gaze suddenly turned deep. “I’ll talk to Sheng Guoning.”

After assigning the tasks for tomorrow, Yi Shi nestled in Lin Heyu’s arms but found it impossible to sleep. The things Lian Jingyuan had instilled in him kept swirling in his mind—knowledge that was hard to digest. He turned it over and over, feeling a vague understanding, but when he tried to chew on it more thoroughly, it seemed ambiguous again.

The cat in the box existed in two states, with two parallel universes, and what was observed was just one of them; the other still existed… If that’s the case, the world where Zhizhi disappeared also exists. They hadn’t experienced it, so they couldn’t be “observed.” Therefore, that photo confirmed that world, while the one they were in was the unobserved parallel world?

It was really giving him a headache. What should he do?

That night, he had that strange dream again, the one he had when he was Xiao Shitou.

In the dream, Lin Heyu was taking the entrance exam for the police academy in Shengzhou, and Yi Shi had left Linjia Village to attend the Third Middle School in Haijing City. He started boarding school in the first year of high school, but because of his personality, he had almost no friends at school. Every day, apart from studying, the thing he looked forward to most was calling Lin Heyu, who was far away in Shengzhou, and chatting for a bit.

“Are you eating well?” Lin Heyu asked, holding his phone while checking the menu released by Haijing Third Middle School that day. “Today there are carrots and onions. Did you secretly throw them away?”

“No,” Yi Shi said guiltily, “…I finished them.”

Lin Heyu didn’t call him out, smiling instead. “Not bad; living alone in the dorm has made you quite sensible.”

Yi Shi sat with his knees hugged in a corner of the playground. “I miss you.”

“I’ll be back for the National Day holiday. You need to be good and not cause trouble at school.”

Suddenly, loud noises came from the phone; Lin Heyu’s classmates were teasing him from behind, asking if he was on the phone with his girlfriend, noting how gentle his expression and tone were. Lin Heyu replied it was family, asking them not to make trouble.

That mention of “family” instantly delighted Yi Shi, as if he had longed for that identity for a long time and it had finally come to pass.

On the eve of the National Day holiday, the students were already daydreaming about their travels, while Yi Shi was methodically packing clothes in his dorm. Suddenly, someone shouted outside, “Yi Shi! Your brother is here!”

Yi Shi immediately dropped the clothes he was holding and dashed out of the dorm, throwing himself at that tall figure. Lin Heyu turned just in time, opening his arms to catch him securely, rubbing his chin against Yi Shi’s forehead. “Looks like you’ve grown taller.”

“I thought I wouldn’t see you until tonight.”

“I had no training this afternoon, so I booked the earliest bus to come back, wanting to pick you up to go home together.”

As the sun set, Lin Heyu held the luggage in his left hand and held Yi Shi’s hand with his right. On the bus, Yi Shi rested his head on Lin Heyu’s shoulder, realizing for the first time how warm the sunset glow was.

This Mid-Autumn Festival coincided with the National Day holiday, and Lin Heyu and Yi Shi went out together to the Southern Cheng’an Cemetery. They bought two bouquets of flowers along the way, one for Chen Shuwu and the other placed in front of the tombstone at Row 15, Number 10, which bore no name, only the surname—Lin.

Wasn’t this originally Lin Heyu’s tombstone? Lin Heyu was right beside him; why did it still exist?

“We’re doing well; you must be very happy over there too.”

“It’s almost the third year of junior high; don’t play too much, or you might not get into the high school you want. Yi Shi is also in the Third Middle School; his grades are much better than yours, so you should learn from him.”

Lin Heyu squatted down, stroking the characters filled with vermilion on the tombstone. “Zhizhi, we really miss you.”

Yi Shi suddenly opened his eyes. The room was dark, and outside the window, the bright moon hung high. When he turned his head, he saw Lin Heyu’s serene sleeping face.

He steadied his mind and carefully recalled the dream’s details. It felt so logical, so real. It seemed the warmth of the sun’s kiss still lingered on his eyelids, and the fragrance of lilies and tulips remained in his palms. It felt like that was not a dream but rather a scene he had truly lived through.

Gradually, his thoughts became clearer: the two different states of the parallel worlds—were indeed real.

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