Qtum (pronounced 'quantum') is an open-source blockchain platform and value transfer protocol that utilizes a proof-of-stake (PoS) consensus mechanism. It aims to amalgamate the strengths of Bitcoin and Ethereum on a single chain. Built on Bitcoin's UTXO transaction model, Qtum incorporates the functionality of smart contract execution and Decentralized Applications (DApps). The platform has recently extended its support to DeFi applications and hosts over 20 tokens on its blockchain. Qtum's unique technologies, the Account Abstraction Layer (AAL) and the Decentralized Governance Protocol (DGP), aim to address issues of interoperability, governance, rigidity, and the costliness of proof-of-work mechanisms.

Qtum operates through a unique consensus mechanism known as Mutualized Proof-of-Stake (MPoS). This mechanism encourages users to keep their coins locked to facilitate and secure block validation, a process known as staking. The right to validate a block is determined by a combination of a user's connectivity to the network and random chance. The block reward is constant and does not depend on coin age, with rewards spread proportionally to the stake. This means the more coins a user contributes to the process, the more they may be compensated. Qtum's Account Abstraction Layer (AAL) integrates the UTXO account layer inherited from Bitcoin with the smart contract layer, inspired by Ethereum. This allows users to build applications and host them on virtual machines, including the Ethereum Virtual Machine (EVM), and the x86 virtual machine.

Qtum aims to provide a general-purpose blockchain that can be used to address a variety of issues found in BTC and ETH blockchain platforms. Its unique technologies, the Account Abstraction Layer (AAL) and the Decentralized Governance Protocol (DGP), allow for the creation and hosting of applications on virtual machines. This includes the Ethereum Virtual Machine (EVM) and the x86 virtual machine. Qtum's compatibility with several programming languages like C, C++, Rust, and Python, makes it a potential platform for developers looking to build and deploy decentralized applications. The platform has integrated common programming libraries in the form of smart contracts.

Qtum was announced and held an Initial Coin Offering (ICO) subsequently, gathering significant resources. The Qtum main chain was released later. Initially, the Qtum coin was issued as an ETH-20 token, but with the launch of the mainnet, it was converted to native blockchain. The project was initiated by Patrick Dai, who studied computer science at Draper University and worked on several blockchain projects before starting Qtum. The other two co-founders are the CTO and blockchain architect Neil Mahi and lead developer Jordan Earls. The Qtum team also includes several high-profile backers, including Roger Ver from Bitcoin.com and Jeremy Gardner, an early crypto investor and co-founder of Augur.