Why a Rollup and not a Bridge?

Rollups provide better security guarantees to a user. Tokens moved to a rollup from a connected layer 1 blockchain can be withdrawn back the layer 1 blockchain without agreement from rollup operator/sequencer (by posting a proof of token ownership onto the layer 1 blockchain). In this way, rollup operators are purely infrastructure providers and not custodians.

Why another Rollup?

This is not just any rollup, current rollups connect to only one blockchain, this rollup – built using our patented technology – connects to multiple blockchains. Our initial launch focuses on three public permissionless blockchains (Ethereum, Polygon, Avalanche c-chain) but it will be expanded to more public blockchains as well as include permissioned blockchains.

Therefore our rollup will allow for the fusion of permissioned and public blockchain networks, including their liquidity.

What use cases can this Multi-Ledger Rollup provide?

See the Use Cases page.

How does Fusion's Mult-Ledger Rollup relate to Fusion's Network of Networks layer?

The Multi-Ledger Rollup is a network available through Fusion's network of network layer. The Multi-Ledger Rollup in turn utilises other networks available through Fusion's network of network layer.

What is the connection to Optimism?

Our Multi-Ledger Rollup extends the Optimism technology stack.

Optimism is a mature and stable tech stack, proven in deployment for many years. Whereas Quant’s blockchain expertise specialises in interoperability. We have therefore decided there is no need to re-invent the rollup infrastructure wheel, instead we focused on making the current Optimism tech stack truly multi-chain in the manner that our patents detail.

Optimism also fully implements the Ethereum Virtual Machine (EVM) and utilises an optimistic rollup style, two features that we viewed as a positive, explained below...

Why utilise the Ethereum Virtual Machine (EVM)?

The EVM is the leading virtual machine for public blockchains as well as a popular virtual machine for permissioned blockchains. It allows any type of functionality to be written into its smart contracts. It has a lot of tooling that will all be reusable for our Multi-Ledger Rollup. For example, transferring any token on the Multi-Ledger Rollup (including QNT) will be possible through the popular Metamask wallet.

Why utilise an Optimistic Rollup?

Firstly there are two types of rollups: (1) Optimistic Rollups and (2) Zero Knowledge Rollups. Both types can have private transactions between users. The differences between the two designs regard how the transitions between blocks are proved. For optimistic rollups, new rollup blocks are assumed to be correct unless proven otherwise. For ZK Rollups block transitions require cryptographic proofs.

At this stage in development we have concluded that utilizing an optimistic rollup design provides us with more flexibility in the way that we can distribute key rollup data (e.g. state roots and transaction batches) across the connected blockchains.

What access controls are we expecting?

• Users will need to register on our platform (Quant Connect) to interact with the Multi-Ledger Rollup devnet, testnet and mainnet.
• Users will need to KYC on our platform (Quant Connect) in order to perform rollup transactions on mainnet.
• Users can deploy smart contracts in different states: public (any user can interact), permissioned (only users whitelisted by the smart contract deployer can interact with it), and private (only the smart contract deployer can interact with it).
• Users will be restricted to the smart contracts that they can set public. Why? We found through project Rosalind that only a small number of contracts (3 in the Rosalind case) can stimulate a vast number of applications, while significantly decreasing the on-chain attack surface. So we have decided to launch with a whitelist for the public contracts, but room for experimentation and bespoke implementations for permissioned and private contracts. Example whitelisted smart contracts for public use will be QRC20 (our ERC20 compatible contract), QRC721 (our ERC721 compatible contract), liquidity pool contracts (for a DEX of our choice – to be announced), a privacy preserving contract, and some others as needed.... This whitelist will expand over time in accordance with feedback. The bytecode and ABIs (interfaces) of the whitelisted contracts will be retrievable from our APIs.

How will privacy work?

The owners of rollup accounts will not be identified. Transaction and data privacy will be implementable via privacy preserving smart contracts, where at least 1 smart contract implementation will be whitelisted for public use.

What liquidity are we expecting?

• Devnet and testnet will be initialised with testnet coins that hold no value.
• Mainnet will be initialised with some tokens from the connected blockchains.
• Some QNT will be moved to the rollup. The main QNT contract will still exist on Ethereum.
• Other tokens moved to the rollup to kickstart the liquidity are to be decided.

Who will be the sequencer?

Quant will be the Multi-Ledger Rollup sequencer, responsible for collecting rollup transactions and building rollup blocks. In the DeFi space it is fairly common to have a single “centralised” sequencer as tokens on a rollup can always be withdrawn onto the connected blockchain by the owning user if there is a sequencer issue.

Who will be the verifiers?

As normal for a Rollup, the data will be placed publicly (in our case across multiple blockchains), therefore any user could recover the state if they wished (but the user will not be able to decrypt private data).

Will you offer a block explorer?

In this Multi-Ledger Rollup, the data you can access and interact with is quite a personal experience, therefore we will not support a block explorer in a traditional sense but we will provide the data relevant to you (balances, transaction history, accessible smart contracts, etc) through APIs and UIs.

What will QNT do?

QNT is the utility token of the Overledger ecosystem, including this latest Fusion expansion. Paying for transactions on the Multi-Ledger Rollup will require QNT, as QNT will be the native token of this rollup, like ETH is the native token of Ethereum.

Additionally, allowing your nodes to be used by the Multi-Ledger Rollup sequencer and verifiers will gain you QNT rewards, while requiring QNT staking.