Transcription of coregulated genes occurs in the context of long-range chromosomal contacts that form multigene complexes. Such contacts and transcription are lost in knockout studies of transcription factors and structural chromatin proteins. To ask whether chromosomal contacts are required for cotranscription in multigene complexes, we devised a strategy using TALENs to cleave and disrupt gene loops in a well-characterized multigene complex. Monitoring this disruption using RNA FISH and immunofluorescence microscopy revealed that perturbing the site of contact had a direct effect on transcription of other interacting genes. Unexpectedly, this effect on cotranscription was hierarchical, with dominant and subordinate members of the multigene complex engaged in both intra-and interchromosomal contact. This observation reveals the profound influence of these chromosomal contacts on the transcription of coregulated genes in a multigene complex.

Detection of the weakest forces in nature is aided by increasingly sensitive measurements of the motion of mechanical oscillators. However, the attainable knowledge of an oscillator’s motion is limited by quantum fluctuations that exist even if the oscillator is in its lowest possible energy state. We demonstrate a technique for amplifying coherent displacements of a mechanical oscillator with initial magnitudes well below these zero-point fluctuations. When applying two orthogonal squeezing interactions, one before and one after a small displacement, the displacement is amplified, ideally with no added quantum noise. We implemented this protocol with a trapped-ion mechanical oscillator and determined an increase by a factor of up to 7.3 (±0.3) in sensitivity to small displacements.

The use of special quantum states to achieve sensitivities below the limits established by classically behaving states has enjoyed immense success since its inception. 1,2 In bosonic interferometers, squeezed states, 3, 4 number states 4-6 and cat states 6 have been implemented on various platforms and have demonstrated improved measurement precision over interferometers based on coherent states. 7, 8 Another metrologically useful state is an equal superposition of two eigenstates with maximally different energies; this state ideally reaches the full interferometric sensitivity allowed by quantum mechanics. 9-11 By leveraging improvements to our apparatus made primarily to reach higher operation fidelities in quantum information processing, we extend a technique 12 to create number states up to n = 100 and to generate superpositions of a harmonic oscillator ground state and a number state of the form 1 √ 2 (|0 + |n ) with n up to 18 in the motion of a single trapped ion. While experimental imperfections prevent us from reaching the ideal Heisenberg limit, we observe enhanced sensitivity to changes in the oscillator frequency that initially increases linearly with n, with maximal value at n = 12 where we observe 3.2(2) dB higher sensitivity compared to an ideal measurement on a coherent state with the same average occupation number. The quantum advantage from using number-state superpositions can be leveraged towards precision measurements on any harmonic oscillator system; here it enables us to track 1 arXiv:1807.11934v3 [physics.atom-ph]