<p>Similar questions have been asked before:</p>

<p><a href="https://bitcoin.stackexchange.com/questions/10938/can-quantum-computing-improve-bitcoin-mining">Can quantum computing improve Bitcoin mining?</a></p>

<p><a href="https://bitcoin.stackexchange.com/questions/13304/can-a-qubit-miner-asic-device-be-created-and-what-would-its-impact-be-on-the-min">Can a Qubit Miner ASIC device be created and what would its impact be on the mining community?</a></p>

<p>However, none of these answers give me a clear indication as to why Grover's algorithm can't be utilized for bitcoin mining. If the current difficulty of bitcoin mining is about 15,466,098,935,554 (approximately 2^44), which means that it would take about 2^44*2^32=2^76 SHA256 hashes before a valid block header hash is found. </p>

<p>However, by implementing Grover's algorithm, it would take only sqrt(2^76)=2^38 hashes to discover a valid block header hash. A 38-qubit quantum computer should be sufficient in this case. Quantum computers of this size have already been built (the largest quantum computer is 72 qubits, to my knowledge). </p>

<p>Therefore, why isn't it feasible to use a quantum computer to mine bitcoin by implementing Grover's algorithm? Did I get something wrong? I'm not too familiar with encryption and quantum algorithms, so please correct me if I missed something......</p>

CC BY-SA 4.0
2020-02-09T22:30:58.297Z
There's no operational quantum computers that can do anything faster than classical computing, you've been deceived by marketing.
Claris
CC BY-SA 4.0
2020-02-10T07:38:12.580Z
"it would take only sqrt(2^76)=2^38 hashes to discover a valid block header hash. A 38-qubit quantum computer should be sufficient in this case."  You are severely confusing time (hashes) with space (qubits) here.
Martin Schwarz
<mining-theory><sha256><quantum-computing>
Why can't Grover's algorithm be used for bitcoin mining?
Biology nerd
# Why can't Grover's algorithm be used for bitcoin mining?

(Asked by: username_0 on 2020-02-09)

Similar questions have been asked before:

[Can quantum computing improve Bitcoin mining?](https://bitcoin.stackexchange.com/questions/10938/can-quantum-computing-improve-bitcoin-mining)

[Can a Qubit Miner ASIC device be created and what would its impact be on the mining community?](https://bitcoin.stackexchange.com/questions/13304/can-a-qubit-miner-asic-device-be-created-and-what-would-its-impact-be-on-the-min)

However, none of these answers give me a clear indication as to why Grover's algorithm can't be utilized for bitcoin mining. If the current difficulty of bitcoin mining is about 15,466,098,935,554 (approximately 2^44), which means that it would take about 2^44\*2^32=2^76 SHA256 hashes before a valid block header hash is found.

However, by implementing Grover's algorithm, it would take only sqrt(2^76)=2^38 hashes to discover a valid block header hash. A 38-qubit quantum computer should be sufficient in this case. Quantum computers of this size have already been built (the largest quantum computer is 72 qubits, to my knowledge).

Therefore, why isn't it feasible to use a quantum computer to mine bitcoin by implementing Grover's algorithm? Did I get something wrong? I'm not too familiar with encryption and quantum algorithms, so please correct me if I missed something......

**Tags:** mining-theory, sha256, quantum-computing

> **Comments:**
> **username_1**: There's no operational quantum computers that can do anything faster than classical computing, you've been deceived by marketing.  
> **username_2**: "it would take only sqrt(2^76)=2^38 hashes to discover a valid block header hash. A 38-qubit quantum computer should be sufficient in this case."  You are severely confusing time (hashes) with space (qubits) here.  

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