Chapter 2

"Sun has already informed me of your intentions. Please follow me," the middle-aged man said as he led them to a black box.

Li Chi had noticed earlier that the ultra-clean lab differed from the outside; instead of large computer cabinets, the room contained various black, opaque boxes. The temperature seemed even colder than the adjacent rooms, causing Li Chi to shiver. "This is what you're looking for," the middle-aged man said, waving his hand. The top of the nearest black box turned transparent, revealing its contents. To Li Chi's surprise, it contained a glass cube, no larger than a man's fist, crystalline and clear.

"The most powerful processor in the world," Sun Yuan murmured in a reverent tone. Suddenly, Li Chi realized what it must be. "This is our prototype quantum processor," the middle-aged man nodded. "It's possibly one of only a few 1024-qubit quantum processors in existence. Only with this many qubits can certain tasks become feasible. Most of the others are likely in the United States. Officer Li, please ensure that no information about this device is leaked, even its appearance is classified."

"You mean…" Li Chi stared at the glass cube, finding it hard to imagine the computational power it held. "That man somehow obtained such a processor and is using it to commit crimes?"

"It's the only plausible explanation," Sun Yuan spread his hands. "The only way he could execute such a flawless man-in-the-middle attack is by exploiting encryption algorithms. But with the combined power of all the world's traditional computers, it would take an eternity to crack a 1024-bit RSA code. So, the conclusion is simple: he must be using a quantum processor to run Shor's algorithm. Current asymmetric encryption algorithms, whether RSA, ECC, or discrete logarithm, cannot withstand it."

"Shor's algorithm?" Li Chi asked. He vaguely recalled the term but wasn't sure of its application. Sun Yuan's tone held a hint of pride. "Yes, it's an algorithm that only quantum computers can use for prime factorization. Existing mainstream asymmetric encryption algorithms rely on the robustness of large prime factorization, a domain that quantum computers can rapidly break."

"So that's what you meant by 'magic.' Given its size, Zhou Tao could indeed carry it around in a bag." Before this case, Sun Yuan had given Li Chi a brief introduction to cryptography. Sun Yuan explained that the essence of cryptography lies in computational asymmetry—you can easily multiply two numbers, but finding their factors from the product is much more difficult. Mainstream encryption algorithms depend on this asymmetry; the encryption process inevitably includes multiplying two large prime numbers. However, breaking it to find the prime factors would take an unimaginable amount of time. Quantum computing, however, changes everything: through quantum parallelism, it factors primes at astonishing speeds.

Li Chi pondered whether he could smash the box and run off with the glass cube, doubting anyone in the building could stop him. "In theory, yes. But there's still a problem," Sun Yuan pointed to the box. "Li, try touching the box's surface." Without hesitation, Li Chi touched it—a sharp, icy coldness radiated from his fingertips, leaving him unsure if the surface was freezing or scalding. He quickly withdrew his hand, tucking his fingers into his pocket to warm them. "Cold, isn't it?" Sun Yuan smiled. "The inside is filled with liquid helium, cooling it to -269°C, about 4 Kelvin. Only at this temperature can the qubits in the processor remain entangled." Sun Yuan gestured to the floor. "Although the quantum processor itself is tiny, the lab's cooling system, which maintains this box at 4K, occupies half a floor."

"So," Li Chi picked up on Sun Yuan's line of thought, "even if he got hold of a quantum processor, he wouldn't be able to carry around this half-floor cooling system."

"Either he has an infinite supply of liquid helium, or he's discovered a way to keep the quantum processor entangled at room temperature. Both are nearly impossible."

"Then aren't we at a severe disadvantage?" Li Chi understood what Sun Yuan was getting at but remained unconvinced. Sun Yuan thought for a moment, about to speak, then hesitated. Finally, he said, "Li, we should leave."

Li Chi gazed at the glass cube, imagining the tasks it could perform. He suddenly realized that there were many more boxes in the room, varying in size.

"Right. By the way, Professor Yao, what's inside these other boxes?"

"I'm afraid I can't answer that. It's classified," Professor Yao adjusted his glasses, his voice flat.

"Then what tasks do you typically run on the quantum processor?" Li Chi pressed on.

"I'm afraid I can't answer that either," Professor Yao paused before continuing, "But, Officer Li, if you catch that criminal, could I participate in the interrogation? I have many questions to ask him."

"That's exactly what we were planning. We'd like to invite you to provide technical support during the interrogation. We'll contact you with the details. But, Professor Yao, are you sure you can't answer my earlier question?" Li Chi persisted.

"Well…" Professor Yao hesitated, "you should be able to guess."

Lowering his voice, Professor Yao added, "But we're licensed."

"Understood." Li Chi nodded. "Sun, let's go."

As they left the lab, Sun Yuan fell silent, lost in thought.

"What were you about to say earlier that you didn't?" Li Chi asked.

"I was thinking about the origin of Zhou Tao's quantum processor. It certainly didn't fall from the sky and hit him on the head," Sun Yuan said as they walked.

Autumn sunlight streamed through the windows into the building's lobby. It was now noon, and the hall bustled with people heading to the cafeteria. The two of them blended into the crowd, appearing no different from a pair of graduate students.

"It couldn't have been stolen from your lab, right? If it had been, you'd have reported it long ago," Li Chi took another sip.

"There have been no reports from within the country, so it's definitely not domestic. It could have come from abroad. And…"

Sun Yuan paused again before continuing, "If he really invented, or somehow obtained, a method to keep a quantum processor entangled at room temperature…"

"What would that mean?" Li Chi asked.

"Then this wouldn't just be an ordinary cybercrime case anymore," Sun Yuan whispered.