"Undercover Alien: The Hat, The Agency, and the Quantum War" leverages today's angst over the possibility that quantum computers will soon threaten modern encryption. This IEEE article below should lay to rest any worries.

Modern Encryption relies on the incredible mathematical difficulty of factoring large prime numbers. So, if a given encryption key requires 2^255 trial decryptions (guesses), which would be typical of an AES-256 key, and you had the fastest supercomputer array on earth (The bitcoin network) to factor it, it would take approximately 1.2x10^49 years. It is so easy to get lost in all those zeros! That's a LOT of years, with a LOT of computers working on it. The age of the universe expressed in SECONDS (5.4x10^-44) is considerably less than that big number. Too many zeros for the human brain to comprehend, I think.
Quantum computers EXCEL at such tasks. That is to say, they can do so exponentially faster than classical computers. Note that word, EXPONENTIALLY! The power of classical computers grows linearly as you add cores, whereas adding qubits to a quantum computer increases the power exponentially. That's the secret. Thus, wIth a big enough quantum computer, it could crack AES almost instantly. But note that disclaimer "Big Enough." That means enough qubits to test all of the possible decryptions in a reasonable time, and that's a LOT of qubits.
The Bitcoin network hash rate is around 186 Million Terahashes/second. A terahash is one trillion hashes. What does that mean? Well, a really, really fast computer desktop computer might hit 20 THOUSAND hashes/second. A good GPU at 2 MILLION H/s will process at around 100x that speed, and dedicated silicon hardware can hit 110 TRILLION hashes/sec. So, the combined power of the Bitcoin network is roughly equivalent to 1.7 million dedicated silicon hardware machines. And all that power would still require far, far longer than the lifetime of the universe to crack today's encryption.
Does that give you an idea how much compute power is involved in breaking encryption?
As Ritz describes it: "Itâ€™s an incredible computational scale. They could not manage it using all the conventional computers on Earth, plus those of millions of other Earths combined. They have replaced and augmented our cloud stack with a quantum computing stack unbelievably far beyond Earth and Asheran technology. It doesnâ€™t exist! It CANâ€™T exist! Itâ€™s unimaginable, impossible, and yet, there it is! Six floors of our building are virtually devoted to the most massive, most complicated quantum computer ever imagined! Like having a blockchain with fifty-trillion-trillion miners all plugging away. More so because itâ€™s quantum-level processing, not classical Von Neumann processing. Unimaginable scale! Incomprehensible scale! Galactic scale!"
Even with the power of exponential math, it will require a VERY BIG and VERY EXPENSIVE quantum computer, one that is far beyond today's technology, to become a meaningful threat. Even when we can build such a computer (many years from now, IMHO) it will cost a lot of money to use it, thus you must be keeping some very valuable secrets to attract such attention. Certainly no one is going to use such a machine to unlock your credit card numbers or your text messages. There are easier and cheaper ways.
Quantum Computing is not, today, a realistic threat to encryption, won't be for a long time, and even we reach a scale where it becomes possible, it will be cost prohibitive for all but the most high profile situations. And, as this IEEE article explains, quantum resistant encryption is being developed.
In short, I am not particularly worried about quantum computing as a threat to modern encryption. I am curious, and will continue to watch the progress, but I see no reason to panic over the prospect of quantum computers. Not until we can build something approaching the one that our villain has built inside the Agency.