Quantum Echoes: What Google’s Breakthrough Means for Q-Day

Dec. 10, 2025

Why in news?

Google’s new Quantum Echoes experiment used a 65-qubit quantum processor to study how information moves around inside a quantum system.
Unlike Google’s 2019 Sycamore experiment, which focused on speed, this work was about understanding how quantum bits behave.
Scientists measured out-of-time-order correlators (OTOC) — tiny echoes that reveal how disturbances travel through a network of qubits.
- Basically, scientists gave the system a tiny “poke,” reversed its evolution, and looked for a small “echo” that came back.
- This echo helped them see how quickly information spreads or gets scrambled among qubits.
These insights can help in studying new materials, superconductors, and chemical reactions.
Even though the research is scientifically important, it does not bring us closer to Q-day — the point when quantum computers could break modern encryption. It poses no threat to security systems today.

What’s in Today’s Article?

Q-Day

Q-day is the future moment when a powerful quantum computer can break today’s commonly used encryption systems.
This doesn’t mean data will be exposed instantly — but anything stolen and stored today could be decoded later once such a machine exists.
- This threat is called “harvest now, decrypt later.”
How Are Governments Preparing?
- Countries are already working on protections.
- The U.S. National Institute of Standards and Technology (NIST) has approved new post-quantum cryptography (PQC) methods designed to stay secure even against quantum computers:
  - CRYSTALS-Kyber → for encryption
  - Dilithium → for digital signatures
- These rely on tough mathematical problems that quantum computers are not expected to crack.
- Experts believe breaking RSA-2048 — a widely used encryption standard — will require millions of stable (logical) qubits.
  - RSA encryption works by multiplying two huge prime numbers.
  - Multiplying them is easy. But figuring out the original primes from the final product is extremely hard — so hard that even supercomputers would need billions of years.
- At current progress, this may take 5 to 8 years, so Q-day is still a future risk, not an immediate one.

How Quantum Computers Work?

Quantum computers use special units called qubits. Unlike normal bits (0 or 1), qubits can be 0 and 1 at the same time (superposition).
They can also be entangled, meaning a change in one instantly affects another, even far away.
Because of this, quantum computers can test many possibilities at once, making them powerful for certain tasks.

Why Quantum Computers Threaten RSA Encryption?

RSA encryption is built on the difficulty of breaking a number into its prime factors — something classical computers take billions of years to do.
But quantum computers can use Shor’s algorithm, which turns the factoring challenge into a search for hidden repeating patterns.
The algorithm uses a special mathematical tool called the Quantum Fourier Transform (QFT) to detect these patterns.
If a quantum computer can run this algorithm on a large scale, it could break RSA encryption exponentially faster than classical computers.

The Problem: Today’s Quantum Computers Are Too Small

Breaking a strong key like RSA-2048 requires enormous quantum machines.
A 2019 study by Google researchers estimated that breaking RSA-2048 needs:
- About 20 million physical qubits
- 8 hours of computation
- Perfect error correction
But today’s biggest quantum machines (Google’s Willow, IBM’s Condor) only have a few hundred noisy qubits.
Why We Need Millions of ‘Logical Qubits’?
- Physical qubits make many errors.
- To perform long, accurate calculations, we need logical qubits — stable units created by combining many physical qubits through error correction.
- A future, powerful quantum computer would need millions of these logical qubits.
- Right now, we aren’t even close to that technology.

Shor’s Algorithm vs. Quantum Echoes: Why They Are Not the Same

Shor’s algorithm is a mathematical tool that could one day break modern encryption by rapidly factoring large numbers — something classical computers struggle to do. Its goal is computational power.
Quantum Echoes, on the other hand, is a physics experiment. It studies how quantum information spreads and comes back like an “echo” inside entangled particles. Its purpose is scientific understanding, not breaking codes.

How Far Are We From Q-Day?

Google’s Quantum Echoes experiment does not make that day arrive sooner.
Instead, it marks progress in understanding how quantum systems behave, not in breaking codes.
The experiment shows that quantum processors are getting better at studying complex interactions inside entangled particles. This is a scientific milestone, not a cybersecurity threat.
While quantum machines are slowly advancing, their biggest potential right now is in understanding nature, chemistry, and materials — not cracking RSA.
The real challenge is making sure our digital systems become quantum-safe before quantum computers eventually reach that power.
The technology is evolving, but so must our defences.