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Platforms based on molecules manipulated using ‘optical tweezers’ might be able to perform complex physics calculations.

Physicists have made the first step towards building quantum computers out of individual molecules trapped with laser devices called optical tweezers. Two teams report their results in Science on 7 December1,2, in both cases making pairs of calcium monofluoride molecules interact so that they became entangled — a crucial effect for quantum computing.

The two papers constitute a “landmark result”, says Adam Kaufman, a physicist at the University of Colorado Boulder. “This opens the door to leveraging entangled states to enhance the potential applications of molecular tweezer arrays.”

Some of the first demonstrations of the basic principles of quantum computing, in the late 1990s, used large numbers of molecules manipulated in a solution inside a nuclear magnetic resonance machine. Since then, researchers have developed a variety of other platforms for quantum computing, including superconducting circuits and individual ions held in a vacuum. Each of these objects is used as the fundamental unit of quantum information, or qubit — the quantum equivalent of the bits in classical computers.

In the past few years, another strong contender has emerged, in which the qubits are made of neutral atoms — as opposed to ions — trapped with highly focused laser-beam ‘tweezers’.

Now, two separate teams have made early progress towards using this approach with molecules instead of atoms. “Molecules have a bit more complexity, which means they offer new ways to both encode quantum information, and also new ways in which they can interact,” says Lawrence Cheuk, a co-author of one of the papers2 who is a physicist at Princeton University in New Jersey. “This offers unprecedented ways for processing quantum information.”

Very cool molecules

Both studies used arrays of optical tweezers with one molecule trapped in each tweezer. Through laser techniques, they cooled the molecules to temperatures of tens of microkelvin, just millionths of a degree above absolute zero. In this state, the molecules were close to being completely still. Their rotation could be stopped, or they could be made to rotate with just one quantum of rotational momentum, called ħ — the smallest rotational speed they can possibly have. Both teams used non-rotating molecules to represent the ‘0’ state of their qubits, and rotating ones to represent the ‘1’.

Calcium monofluoride is highly polar — the negative electric charges carried by its electrons cluster towards the fluorine atom, leaving the calcium end of the molecule with a net positive charge. The researchers could coax two calcium monofluoride molecules to interact by ‘feeling’ each other’s positive and negative poles. “The dipolar interaction of molecules gives us an extra tuning knob,” says John Doyle, a physicist at Harvard University in Cambridge, Massachusetts, who co-authored the other paper1.

In this way, the team was able to demonstrate that the molecules became entangled, meaning that they formed a collective quantum system. This is required for quantum computers to run algorithms.

For most applications, molecular quantum computers will be slower than those using other types of qubit, researchers say. But molecules could be a natural environment in which to manipulate quantum information using ‘qutrits’, which have the three possible states: −1, 0 and +1. Qutrits could offer a way to carry out quantum simulations of complex materials or the fundamental forces of physics.

Doyle adds that these advances could also help in the use of trapped molecules for high-precision measurements that could reveal the existence of new elementary particles.

The work "highlights the phenomenal rate at which this field has advanced," says Hannah Willams, a physicist at the University of Durham, UK. "With this achievement, they have shown that molecules will be the basis for a competitive platform capable for quantum simulation."

doi: https://doi.org/10.1038/d41586-023-03943-1

Communist party Politburo promises ‘proactive’ fiscal and ‘effective’ monetary policy to support growth

President Xi Jinping has warned that China’s economic recovery is “still at a critical stage” as Communist party leaders pledged to support growth with further “proactive” fiscal and “effective” monetary policy in the new year.

The comments follow months of mixed data in the world’s second-largest economy, with exports in dollar terms turning slightly positive in November after a long dip, while official data suggested manufacturing activity was weakening.

In a speech to a political gathering in Beijing, Xi said that although the economic recovery from the pandemic was improving, it faced an adverse international political and economic environment and overlapping domestic cyclical and structural challenges.

“At present, our country’s economic recovery is still at a critical stage,” the state news agency Xinhua on Friday quoted Xi as saying in the speech earlier in the week. “The development situation facing our country is complex.”

China’s economy has struggled to rebound from the impact of strict Covid controls imposed last year and a deep liquidity crisis in the property sector that have undermined growth and investor and consumer confidence.

The government has gradually stepped up monetary and fiscal stimulus, cutting interest rates and announcing the issuance of Rmb1tn ($140bn) in central government bonds, but the pick-up in activity has been slow and uneven.

Separately, the Communist party’s Politburo declared at a meeting held on Friday to discuss economic work for the coming year that the government should “continue to implement proactive fiscal policies and prudent monetary policies”.

It said Beijing should improve “the quality and efficiency” of fiscal policies while monetary policy should be “flexible, appropriate, precise and effective”, Xinhua reported.

The meeting also said it was “necessary to . . . strengthen economic propaganda and public opinion guidance”. Economists have complained of growing pressure from Beijing not to talk down the economy this year.

Following a sharp rise in youth unemployment, the National Bureau of Statistics this year also discontinued a data series on joblessness among the young.

Xinhua did not reveal whether the Politburo discussed next year’s official gross domestic product growth target. This is usually announced in March at the annual meeting of China’s rubber-stamp parliament and is one of the most keenly anticipated policy decisions in the country’s economic calendar.

Beijing this year set the target for GDP growth at 5 per cent, its lowest in decades. Economists speculate it might set the same level for 2024, though they warn substantial stimulus would be needed to achieve this growth given the lacklustre momentum in the economy.

Citi analysts said in a research note that the language from the Politburo showed a shift in its policy bias towards “progress”, which includes economic growth, after many years in which Beijing stressed “stability”.

“We have long been arguing that development should be a pre-condition for stability, national security and geopolitical agendas,” the analysts wrote. They predicted Beijing would set a target of 5 per cent next year, but warned there would be no “mega stimulus”.

HSBC Greater China economist Erin Xin said in a research note that in addition to policies to boost the housing market, “we expect Beijing to continue to increase fiscal support while monetary policy is likely to remain accommodative”.

“China’s domestic demand recovery still needs more support,” Xin wrote.

The Politburo meeting also called on cadres to step up an anti-corruption drive in the new year, particularly to “seriously investigate and deal with . . . ‘flies and ants’” — a term for corrupt local government and state enterprise officials.

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The Competition and Markets Authority (CMA) is today providing an early opportunity for the parties and interested third parties to comment on whether the partnership between Microsoft and OpenAI, including recent developments, has resulted in a relevant merger situation and, if so, the impact that the merger could have on competition in the UK.

The Invitation to Comment (ITC) is the first part of the CMA's information gathering process and comes in advance of any launch of a formal phase 1 investigation.

The speed at which artificial intelligence (AI) is scaling across use cases and markets is unrivalled in economic history, while advances in powerful foundation models (FMs) mean that this is a pivotal moment in the development of this transformative technology. The CMA's recent report into the rapidly evolving market for FMs noted both opportunities and risks for competition and consumer protection, which were captured in a set of proposed principles to guide the development of the market toward positive outcomes for people and businesses. Critical among these is the need for sustained competition between AI developers which will help to deliver innovation, growth and responsible practices across the sector, as well as the need for open and effective competition in the deployment of FMs across a range of downstream activities.

As part of its ongoing work in this area, the CMA has been closely monitoring the impact of partnerships and strategic agreements which could result in a weakening of competition in the development or use of FMs. The partnership between Microsoft and OpenAI (including a multi-year, multi-billion dollar investment, collaboration in technology development and exclusive provision of cloud services by Microsoft to OpenAI) represents a close, multi-faceted relationship between two firms with significant activities in FMs and related markets.

There have recently been a number of developments in the governance of OpenAI, some of which involved Microsoft. In light of these developments, the CMA is now issuing an ITC to determine whether the Microsoft / OpenAI partnership, including recent developments, has resulted in a relevant merger situation and, if so, the potential impact on competition.

The CMA will review whether the partnership has resulted in an acquisition of control - that is, where it results in one party having material influence, de facto control or more than 50% of the voting rights over another entity - or change in the nature of control by one entity over another.