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Optical Computing Reduces Energy Requirements for Cryptocurrency Mining | Technology News | July 2023
Researchers at Stanford University have developed a light-based processing scheme using photonics integrated circuit to reduce the energy needed for cryptocurrency and blockchain applications. Mining cryptocurrencies like Bitcoin, a process of verifying transactions and adding new cryptocurrencies to the blockchain, consumes up to 1% of the world’s energy. This energy expenditure is expected to increase as cryptocurrencies and blockchain applications become more widespread.
Cryptocurrencies are digital currencies created using encryption algorithms. These alternative currencies require a blockchain, a type of digital ledger that records information such as transactions in a way that is difficult or impossible to modify or hack.
Researchers have developed a new light-based computing scheme called LightHash that reduces the energy needed for cryptocurrency and blockchain applications. First author Sunil Pai is pictured with the optical setup used for the new research. Courtesy of LightHash.
“Currently, cryptocurrency mining is only accessible to those with access to highly discounted energy, below $0.05/kWh,” said first author Sunil Pai, who performed the research at Stanford and is now at quantum IT company PsiQuantum. “Our energy-efficient chips will enable individuals around the world to profitably participate in mining.”
The scheme is called LightHash. It uses a photonic integrated circuit to create a photonic blockchain. With further development, the researchers believe that this approach, if implemented on a large scale, could create approximately a tenfold improvement in power consumption compared to the best modern digital electronic processors.
“Our photonic blockchain approach could also be used for applications beyond cryptocurrency, such as secure data transfer for medical records, smart contracts and voting,” Pai said. “This work paves the way for low-power optical computing, which can ultimately reduce data center power consumption.”
Growing concerns about the large amount of energy needed to mine cryptocurrencies have led some popular ones, such as Ethereum, to turn to unproven and potentially insecure methods to minimize their carbon footprint.
To find a greener approach while maintaining a high level of security, Pai and colleagues used silicon photonics to reduce the energy needs of cryptocurrency networks. LightHash improves on a scheme previously developed by the team called HeavyHash, which is currently used in cryptocurrency networks such as Optical Bitcoin and Kaspa.
“The main motivation for LightHash was HeavyHash’s high sensitivity to hardware errors,” Pai said. “Because analog computers, including photonic ones, struggle to achieve low error rates, we designed LightHash to maintain all of the security properties of HeavyHash, while improving its robustness to errors.”
The new scheme creates a photonic blockchain using a photonic integrated circuit, the small metal rectangle. Courtesy of LightHash.
Creating Bitcoin securely or managing your own computer network requires processing a hash function such as SHA256 or HeavyHash to transform input data into a single output number in a way too complex to reverse, which accounts for most of Bitcoin’s energy consumption. In the new work, the researchers modified HeavyHash to work with a co-designed silicon photonic chip carrying a 6×6 network of programmable interferometers. This enabled low-energy optical processing of matrix multiplications, which makes up the majority of computation in LightHash.
To evaluate the feasibility of using LightHash for matrix multiplication, the researchers built an optical rig to control and track light propagation by tuning heating elements and viewing lattice points on an infrared camera. They also implemented an error mitigation algorithm and established feasibility criteria for scaling the technology.
The experimental results obtained with the silicon photonic chip corresponded to those obtained using the simulated error predictions.
“Our results suggest that LightHash can be feasibly computed at scale using current silicon photonic chip technology,” Pai said. “Essentially, we devised a way to use analog optical circuits to perform multiplications with near-zero power dissipation but with sufficient precision for use in a digital encryption scheme.”
In order for LightHash to demonstrate significant advantages over digital equivalents, it must be scaled up to 64 inputs and outputs. Researchers are also working to further reduce energy consumption by designing low-power electromechanical tuning elements and energy-efficient converters to transform optical signals into electrical signals.
They say that because the new chip accelerates matrix multiplication, the most computationally intensive operation for artificial intelligence applications, it could also help make the training and application of photonic neural networks more computationally efficient. energy view compared to conventional digital implementations.
“It will be interesting to see how cryptocurrency technology evolves and to what extent photonics can contribute to the increasingly widespread role of decentralized ledgers in today’s society,” Pai said.
The research was published in Optica (www.doi.org/10.1364/OPTICA.476173).