Bitcoin vs. Quantum Computers: Why 1.9 Billion Qubits Stands Between Now and Crypto’s Biggest Fear
TL;DR
A viral Reddit discussion in r/CryptoCurrency is making the rounds, and the headline number is striking: breaking Bitcoin’s cryptographic security would require approximately 1.9 billion qubits. The best quantum computers publicly available today — including IBM Quantum’s cutting-edge processors — operate at only a few thousand qubits. That’s a gap of roughly six orders of magnitude. So while the quantum threat to Bitcoin is real in theory, the timeline for it becoming a practical danger is far longer than most headlines suggest. The community is divided, though, on whether “far away” means “not worth worrying about.”
The Number Everyone’s Talking About
If you’ve been anywhere near the crypto corner of the internet lately, you’ve likely seen the post. A thread in r/CryptoCurrency titled “Breaking Bitcoin would require 1.9 billion qubits. The best quantum computer today has a few thousand. So where’s the real risk?” racked up 235 upvotes and sparked 243 comments — a clear sign this topic struck a nerve.
The core premise isn’t new, but the framing is refreshingly direct: the quantum threat to Bitcoin is often discussed in breathless, apocalyptic terms, but the actual numbers tell a more nuanced story. You’d need 1.9 billion qubits — functioning, error-corrected, fault-tolerant qubits — to crack the elliptic curve cryptography underpinning Bitcoin addresses. Today’s best machines? A few thousand.
Let that sink in.
That’s not a gap you close in a year or two. That’s not even a gap you close in a decade at current rates of progress. But here’s where the community disagrees: does “a very long time from now” mean we shouldn’t care today?
What the Sources Say
The Consensus
The Reddit community largely agrees on the raw physics. The 1.9 billion qubit figure isn’t a number someone invented to be reassuring — it reflects the genuine computational overhead required to run Shor’s algorithm (the quantum algorithm capable of breaking elliptic curve cryptography) against Bitcoin’s 256-bit keys within a timeframe that would actually be useful for an attacker.
The distinction the community draws is between physical qubits and logical qubits. Current quantum hardware is noisy — errors creep in constantly, and you need many physical qubits to encode a single reliable logical qubit through error correction. The 1.9 billion figure refers to physical qubits under realistic error-correction assumptions. This makes the bar even higher than it might initially appear, and it’s a point that consistently comes up in the thread as a reason not to panic.
IBM Quantum, widely recognized as operating some of the most powerful publicly accessible quantum processors in the world, is the benchmark reference here. When we say “a few thousand qubits,” we’re talking about systems in that class — state-of-the-art by today’s standards, but nowhere near the territory required for cryptographic attacks on Bitcoin.
Where the Community Disagrees
The debate gets interesting when it moves from “can they break it now?” to “when should we start worrying?” This is where the Reddit thread’s 243 comments reveal genuine disagreement.
Some commenters take the optimistic read: the gap is so enormous that Bitcoin has plenty of time to adopt post-quantum cryptography before any real threat materializes. Proposals for quantum-resistant signature schemes exist, and the argument is that the Bitcoin ecosystem will upgrade its cryptography long before quantum computers reach threatening scale.
Others push back on this complacency. Their concern isn’t about Bitcoin being broken today — it’s about harvest now, decrypt later strategies. A sufficiently motivated state-level actor could theoretically record encrypted Bitcoin transactions on the blockchain right now, store them, and decrypt them once quantum hardware catches up. For most users this is academic, but for wallets holding significant amounts — especially older wallets with exposed public keys — this is a legitimate long-term concern.
There’s also a subtler disagreement about the pace of quantum progress. Quantum computing has a history of hype cycles, and some community members are skeptical that progress will follow the exponential curves that quantum optimists project. Others point out that even slow, steady progress eventually gets you to a very large number, given enough time.
The Qubit Gap in Context
To appreciate just how large the gap really is, it helps to frame it concretely.
The best publicly accessible quantum computers today, including those on IBM Quantum’s platform, operate at the scale of a few thousand qubits. Let’s be generous and say 5,000 — that’s roughly where cutting-edge public systems sit as of early 2026.
To reach 1.9 billion qubits from 5,000, you’d need to multiply today’s qubit count by 380,000 times.
If qubit counts doubled every two years — a very optimistic assumption that may not hold at scale — you’d still be looking at roughly 35+ years before reaching that threshold. And that’s before accounting for error correction requirements, decoherence challenges, and the engineering difficulties of scaling quantum hardware in ways that maintain quality, not just quantity.
This isn’t meant to dismiss the quantum threat — it’s meant to contextualize it. The r/CryptoCurrency community is doing something valuable by putting hard numbers on the table rather than vague warnings about “quantum supremacy.”
Pricing & Alternatives
The source package references two key platforms relevant to tracking this space:
| Platform | Description | Pricing |
|---|---|---|
| IBM Quantum | Home to some of the most powerful publicly accessible quantum processors; the primary public benchmark for current quantum hardware capabilities | Not publicly listed |
| CoinGecko | Crypto data provider covering market prices, on-chain metrics, and educational content about cryptocurrencies including Bitcoin | Not publicly listed |
Neither platform’s pricing data was available in the source material. IBM Quantum does offer access tiers ranging from free educational accounts to enterprise research partnerships, though specific current pricing wasn’t included in the sources reviewed. CoinGecko offers both free and premium data tiers for crypto market intelligence.
For anyone wanting to track the quantum computing landscape as it relates to crypto, IBM Quantum’s public research publications and CoinGecko’s educational resources are both worth bookmarking.
The Real Risk: It’s Not What You Think
Here’s the thing — the Reddit thread’s framing is clever precisely because it reframes the question. The headline grabs you with the 1.9 billion qubit figure, but the real payload is the second half: “So where’s the real risk?”
Based on the community discussion, the consensus answer isn’t “there is no risk.” It’s “the risk is real but mislocated in time and type.”
The most credible near-term risks aren’t about breaking Bitcoin’s cryptography at all. They’re about:
Exposed public keys: Bitcoin’s security model keeps your public key private until you spend from a wallet. Old-style “pay to public key” (P2PK) addresses — used heavily in Bitcoin’s early days, including by Satoshi Nakamoto — have their public keys permanently visible on-chain. These are technically more vulnerable once quantum hardware advances significantly, even if the timeline is still very long.
Complacency about protocol upgrades: Bitcoin has upgraded its cryptography before (the move toward Taproot being one example), but any future migration to post-quantum signature schemes would require broad ecosystem coordination. Waiting until quantum hardware is actually threatening before initiating that process would be dangerously late.
Narrative risk: Even if quantum computers can’t break Bitcoin technically, the perception that they might could cause significant market disruption. FUD doesn’t need to be accurate to move prices.
The community thread captures this nuance well. The 1.9 billion qubit figure is reassuring for today. Whether it remains reassuring in 20, 30, or 40 years depends on how quantum hardware scales and, critically, whether Bitcoin’s cryptography evolves in parallel.
The Bottom Line: Who Should Care?
If you’re a regular Bitcoin holder with a standard wallet: The quantum threat is not your immediate problem. The gap between current hardware and what’s needed to threaten your holdings is vast, and there will be ample time for protocol-level responses before this becomes acute.
If you hold funds in old P2PK addresses or have reused Bitcoin addresses extensively: The picture is slightly more nuanced. You’re not in danger today, but it’s worth understanding that your public keys are permanently exposed on-chain, and long-term quantum risk applies more directly to your situation than to standard modern wallets.
If you’re building Bitcoin infrastructure, running a node, or involved in protocol development: This is very much your problem, just not urgently. Post-quantum cryptography research and the eventual Bitcoin upgrade path deserves attention now — not because the threat is imminent, but because protocol changes at Bitcoin’s scale require years of research, debate, and coordination.
If you’re a quantum computing researcher or investor: The r/CryptoCurrency discussion is a useful reality check on public expectations. The community is increasingly sophisticated about qubit counts and error correction — you’ll need to bring real numbers to any narrative about quantum threats to crypto.
The 1.9 billion qubit figure is one of the clearer, more honest framings of the quantum-Bitcoin relationship that’s circulated in the crypto community. It deserves more attention than the typical vague “quantum will kill crypto” or “quantum is decades away, don’t worry” takes that dominate mainstream coverage.
The threat is real. The timeline is long. The time to start thinking about it is now — not to panic, but to plan.